The Research Processes of
few years ago Stephen Stoan argued that librarians approach research
from a very different angle than do researchers.(n1) He asserted that
the steps that librarians, as generalists and tool specialists, go
through in pursuing the answer to a reference question are very
different than the processes scholars go through when they do research.
Yet the process we tend to teach in library instruction--the "search
strategy" described to students--most often resembles the librarian's
approach: making a systematic, tool-based series of searches that takes
the student from a general background source through monographic and
periodical literature.(n2) This instruction may be embedded in a
discussion of the larger research process, which includes analysis of
research topics and evaluation of materials found, and it may be
introduced in the context of the growth of a discipline or the
structure of its literature. Regardless of its context, however, the
portion of library instruction that deals with finding materials tends
to emphasize a sequential, tool-oriented search technique.
Library Instruction Critics
students who are initiates in disciplines, not experts, do not go about
research the same way that their professors do. They cannot make the
connections and the critical judgments that are second nature to
specialists, nor are they familiar enough with the discipline to easily
recognize a valid or useful research question. Given these limitations,
some librarians suggest we can't really teach undergraduates to do
research. Stoan suggests that we should "keep in mind the very limited
purposes of instruction in bibliographic resources" and should "be
careful not to equate library skills with research skills.(n3) Richard
Feinberg and Christine King warn against the hubris of equating library
instruction with the development of students into life-long learners,
and recommend we stick with short-term library skills.(n4) And recently
Tom Eadie suggested that library instruction, however we teach it, is
simply a waste of time.(n5) He contends that it presumptuously
"provides the answer before the question has arisen"(n6) and suggests
that the questions, once raised, can be more efficiently answered at
the reference desk than by library instruction, which he characterizes
as a one-size-fits-all lecture, or "a fifty-minute oral
All of these commentators appear
to find little connection between research and library skills. The
assumption is that we should (at most) teach skills and leave the
teaching of research to specialists, if it is to be taught at all. In
fact, all of these critics seem to call into question the notion that
undergraduates do research at all, and challenge the place of research
in an undergraduate curriculum. Eadie even evokes a past when reserve
readings satisfied the undergraduate's library needs and the library
functioned quite adequately without bibliographic instruction and with
minimal reference service--and, as he remembers it, it worked just
These critics are selling the goals of
our institutions short. Leaving students to flounder on their own--or
simply teaching the skills required to find materials for a single
library-related assignment--is not doing justice to our students or to
the educational aims of our institutions. Furthermore, it doesn't make
sense to teach disparate library skills without putting them in the
context of the research process. The students in our classrooms want to
see some pattern behind the skills, want to see how the pieces fit
A Better Approach
what process should we teach? On the one hand, if we teach research as
a process of systematically working through finding tools, we are
misrepresenting the nature of research--it isn't finding bibliographic
items that counts, it is the interaction of ideas and the emergence of
new ones through that interaction. On the other hand, we can't draw
from the expert model because that model assumes a thorough knowledge
of the discipline. If we are to describe research as a process, we need
to address the special kinds of problems encountered by undergraduates,
novices to disciplines, who are striving to see the shape of the
discipline, to tap into its interconnections, to determine what might
constitute a valid research question and to frame an acceptable
response. We need to teach those skills that will facilitate
integrating library use into the entire research process.
Mellon and Carol Kuhlthau have both made contributions to understanding
the library search component of the research process. Mellon focuses on
the way in which the writing process and research are recursive;
Kuhlthau examines the cognitive and affective aspects of the research
process for high school students.(n9) In both cases the authors have
found that research is not a straightforward application of tools in a
systematic fashion, but an interplay of a variety of factors in which
information collection plays an integrated part. This study attempts to
build on theft work by developing a more detailed understanding of
actual research experiences by students who, by all accounts, performed
uncover the process students go through when they are engaged in
research, faculty in a number of different departments were asked to
identify students who had successfully completed research projects of
various sorts. Fourteen of these students agreed to participate in
in-depth interviews in which they were asked to describe how they found
a focus for their research, what the major parts of the process were,
how they retrieved, evaluated, and made use of sources, and how the
research process related to the writing process. (See Figure 1.) This
interview approach was modeled on an important study in the composition
field in which Janet Emig asked several students to compose a piece of
writing while describing the process aloud.(n10)
relying on the students' hindsights decreases the reliability of the
results of this study--recollected and self-reported data usually
suffer from bias--it was decided that observing students during the
research process or recording theft comments on the process as it
happened would be too intrusive and too lengthy a procedure. Direct
observation was thus sacrificed for what hopefully would be the
outlines of a picture of undergraduate-level research. The data were
not expected to provide definitive answers, but it was thought that it
would raise some interesting questions that could be addressed with
more rigorously controlled methods.
The goal was to
compare the process described in the classroom as research--either the
library model, with its emphasis on tools, or the expert model
described by Stoan, with its emphasis on familiarity with the
literature--with the research students actually do. The suspicion was
that neither model was an accurate one for undergraduate research.
students interviewed were astonishingly articulate about theft
research, and were happy to share both successes and dead ends. The
students ranged from freshmen to seniors and were engaged in a variety
of projects, including:
The departments involved
included political science, physics, art history, music, philosophy,
education, and management. None of the assignments were mere reports
based on library sources; each required that the student either
manipulate original data or provide an original hypothesis.
Formulating a Focus for Research
having students describe theft projects the interviewer asked them
questions about their focus, and asked them to draw a time-line of
their research to get a sense of how long each stage in the research
process lasted. Generally speaking, getting a focus for research was
the most challenging and the most time-consuming part of the entire
project for the students, even for those who had fairly structured
assignments. The focus seemed to be generated in one of a number of
ways. For some students, the research project was the culmination of a
long-standing interest. As one student put it:
this case the student was approximating the "expert" status of the
expert researcher model--she was able to determine a focus quickly
because she already knew the subject well enough to know what a valid
question about it would be. A twist on this is the student who, though
not an expert in the subject, draws on some expertise to ease into the
new territory. One student with a double major chose a focus that
involved both majors: "I wanted to tie as many courses together as I
possibly could." Though she had never dealt with her subject before, it
was a subject that she could approach from the disciplines in which she
had some training.
Other students had more spade
work to do before they could find a focus. They were truly novices
working in fields they knew little about. One student, given a fairly
structured assignment, knew what topic she was to write about, but
didn't know how the field itself viewed the topic, which questions were
considered interesting and valuable by practitioners in the field. She
did a scan of recent literature using an appropriate subject abstract
and, because she began to see that there was considerable interest in
one aspect of the topic, was able to choose a focus that reflected the
current interests of the discipline.
student said he "just started nosing around a little bit" by browsing
in the book collection and dipping into some of the books he found. He
came up with a topic area that looked promising, then took it to his
instructor to get her opinion of whether there was research potential
in the topic. He did not get a clear focus until much later, but worked
toward it by becoming increasingly familiar with the literature
covering his topic area. Over time, he recognized valuable material as
he encountered ideas and names repeatedly: "At least you know what you
should be looking for." His approach was to gradually map the scope and
features of the topic by increasing his mastery of its literature.
number of students reported that their instructors were excellent
interpreters of the field; they would ask their instructors for a nudge
in the right direction by bringing them a broad topic and asking them
about current "hot" questions and authorities in this area. "I got an
article.., that was really helpful," said one student. "A lot of times
that happens. You go to professors and they tell you a name . . .
that's the most helpful." Significantly, it was the subject expertise
of instructors that students tapped for sorting out current authorities
and major studies; librarians were generally not approached in this
stage of becoming familiar with the field.
One student expressed reservations about doing too much
reading in secondary sources before finding a focus:
one difference between her situation and the other students' was that
her teacher had been very explicit in defining what kind of research
questions were valid for the field and had given the students a source
list to start with. None of the other students had that advantage.
single factor that most frequently spurred a student's movement from
the preliminary, focus-setting phase into a more directed phase was the
need to verbalize a focus. Many of the students were required to hand
in a written proposal or research design, and all who did reported that
this requirement was essential to forming their focus. Either the
activity of writing the proposal or the ensuing feedback from the
instructor clarified the focus for them. As one student said: "Putting
it in words definitely formalizes it .... It's almost like you have to
practice using the words.., it makes more sense that you get your
practice and then go back.., where it really counts . . ."
a research proposal can help students define a problem once they are
familiar enough with their topic to recognize a legitimately
interesting question, and once they realize that definition of the
problem helps identify the kinds of information needed. The student
moves from being familiar with the topic area to seeking specific kinds
Gathering Evidence, Reformulating the Focus
techniques students used to search for materials changed over time. In
the first phase, before students had determined a focus for their work,
they browsed widely, scanned abstracts or indexes for interesting
titles (or, in one case, scanned indexes to verify a hunch that an area
had been neglected by the field), and talked with classmates and their
instructors about possibilities. In the second phase, after they had
some angle from which to view the material, they often backtracked,
returning to things they had looked at briefly, able to interpret them
differently. One student reported that he had "run across some things"
in his preliminary research that would later prove critical to the
success of his research, but "I didn't realize it yet because I wasn't
familiar enough with it."
Using key sources.
Several students reported that finding a key source was a pivotal point
in their research; these sources were useful in a variety of ways,
sometimes helping them to clarify their questions, sometimes
legitimizing a question for them by illustrating that others were
interested in the same idea, and sometimes giving them the appropriate
vocabulary used in the field for their questions. Quite often, too,
these key sources provided a gateway into a whole network of
information in the form of references.
this stage were more likely to tap into the citation network, and often
seemed to feel a part of that network, as if they had joined a
community of scholars who jointly tackled an area of research. Students
were likely to refer to an idea by the name of the researcher
responsible for developing it. Many of them demonstrated a
sophisticated understanding of the relationship between sources,
reporting that they saw patterns in citations, that some names were
cited very frequently, that one work had changed the way the entire
field examined an issue, or that some researchers demonstrated one bias
or another. And, though students made use of finding tools such as the
online catalog, indexes, and abstracts, they tended to believe that
citations--either those given as references in works or those provided
by their instructors--were their most direct and useful route to good
material. It is through this web of connected ideas--what Stoan refers
to as "the primary literature [indexing] itself"(n11)--that these
students could see the shape of the discipline emerge. As one student
used the materials they found for a number of different purposes: as
sources of information, ammunition for their arguments, and examples of
writing within a given discipline. As examples, these sources serve as
a kind of template for format, a key to elements that might go into an
argument in a given field, and a model of what evidence is used to
support such arguments.
When asked how they evaluated sources, students described a number of
criteria. Relevance was typically the first criterion used for
screening sources. One student said: "When I got a book I'd flip to the
table of contents and start looking.., at headings that were possibly
interesting and relevant." Currency was another criterion frequently
used for screening. Then, the intended audience of the written work was
frequently examined. Students who were given assignments in which they
were to synthesize ideas and find major points tended to screen out any
works that were too detailed or technical. The others valued sources
that demonstrated that the author was working within a given field
using the conventions of scholarship for that discipline. They checked
the language of the article to screen out those works addressed to a
Finally, a number of students
described ways in which they assessed the quality of a given work.
Several mentioned the importance of finding an article or author cited
by others, one saying that he used citations "to take a tally of how
often a certain article was used." Some looked at citations to check
whether or not a writer had used appropriate evidence and rejected
those that did not seem aware of major studies or failed to produce
evidence for their assertions. Others mentioned the publishing house or
the reputation of a journal as a screening factor. One student, a
senior quite familiar with her field, said: "I didn't want to stray
into weird journals." But when researching in another field in which
she lacked expertise, she relied on relevance as her major criterion
for journal quality. "If the title [of an article] sounded good, I read
it," even without knowing the reputation of the journal.
also relied on their instructors' judgments in evaluating sources:
"It's important to keep communication open with your [professors] about
that, because they know.., they're in that network."
Dealing with contrast.
Many students found sources that contradicted one another or the
student's thesis; they tended to look on this experience positively.
One student confessed that she sometimes wanted to "throw away that
notecard" if the source undermined her argument, but felt it would be
unfair to fail to represent both sides of an issue. Another said that
opposing pieces helped her formulate her own opinion because they gave
her something concrete to refute. A third said contradictory analysis
"was exactly what I wanted" because "the basic idea was to present the
contrast.., you want contrast."
While one student
said "there's a lot of different theories out there, so... I just
looked for things that fit what I was thinking," another student used a
very different approach:
almost all of these students--except for one who had a very brief
assignment and another who was preparing a practice-teaching
unit--writing was an ongoing process, not a separate and final stage.
Students frequently did some writing before getting deeply into
research, keeping notes, making analyses, organizing materials, writing
proposals to articulate theft project, and often writing theft first
draft in several stages. Few of the students saw any clear distinction
between research and writing; they saw them as aspects of a single
activity, concurrent and integrated. One student reported using the
following techniques to get her ideas flowing.
said: "I really like to articulate my idea and get my thesis going
because then I keep it with me and I constantly look at it. I have it
memorized, so I never get too far away from what I'm supposed to be
Many students reported that their
instructors demanded some form of written material before the final
draft, and they found that very useful in formulating a solid topic and
getting essential feedback before it was too late. At least ten of the
fourteen students had written work reviewed by their instructor long
before the research process was over, and, without exception, found the
early feedback--and the early deadline--valuable.
used a variety of methods for keeping notes on their material. Some
preferred to have verbatim excerpts from sources, either hand-copied or
photocopied. Others used a kind of double-entry system: text from
sources on one side, analysis on the other. As one student put it: "If
I just have this abstract quote--so what? I find that articulating how
it relates right away is really important."
varied a great deal, too, in organizing material in preparation for
writing a draft of the final product. Fewer than half used outlines,
and those were most typically students writing a short paper. Others
organized their material using nonlinear structures, one sorting her
notecards in a wheel, with her thesis in the middle and all of her
major points radiating out from and referring back to the thesis.
"Everything, then, becomes like a network or a web instead of like a
long rope." Still others, particularly those working on papers of 20
pages or more, wrote their papers in sections at different points in
the semester, and in many of these cases weren't exactly sure, at the
beginning, where their project was headed. In their experience, an
outline would have been impossible because they discovered what they
wanted to say as they wrote.
Students used a
variety of methods for bringing evidence into their writing. Some had
notecards with quotations and analyses that they sorted into logical
piles--piles that then became the major sections of their work. Others
discovered as they wrote that they needed evidence, and would seek it
out at those points. One student had gathered quotations to support
sections of her paper about which she felt the least confident, but
accumulated supporting information on an as-needed basis for the rest
of the paper: "When I needed information [on a specific area]... I
would go back and browse through various writers to see how they
Another made writing and research an integrated activity.
most students this approach would be too difficult to control, but in
his case it seemed to work; he went on to present his paper at a state
research conference. There was only one instance in which a student
organized her ideas in the form of an outline and followed it for the
final written product. In all other cases the students found composing
a process that tended to generate its own direction.
Conclusions and Recommendations
results of this study suggest fruitful ways to rethink some of the
assumptions that underlie teaching students to do research. Two
findings were particularly striking: the large proportion of time and
energy the students spent formulating a focus, and the diverse tactics
students used to successfully negotiate that phase of research. Another
surprise was the way in which these students perceived their sources.
They had a sophisticated understanding of the nature of research, of
the need to construct a response based on evidence rather than merely
finding information and reporting on it. The rhetorical aspect of
research writing-selecting information to support an argument that will
persuade a particular audience, and relating one's own ideas to the
wider world of available interpretations--was a constant concern in
these students' use of information. And finally, it was interesting to
see the variety of ways in which students integrated research and
writing, and the various forms in which writing occurred throughout the
More specifically, the study
raises questions about the teaching of research, both in terms of
assumptions about the place of library skills in the entire research
process, and in terms of which skills should be taught in the context
of research. As expected, this study generated far more questions than
answers. Some tentative conclusions and recommendations for further
Research comes in many different packages.
These students were engaged in a wide variety of assignments involving
research. In fact, many of the faculty first contacted for suggestions
for student subjects for the study said they didn't give "library
research assignments." We persuaded them that we were looking for
students engaged in writing more than what they consider a "traditional
research paper"--the kind of paper that one faculty member described as
an uncritical "cobbling together of secondary sources; an invitation to
plagiarism." If we truly want to be involved in teaching research
skills, we must not assume that research assignments are driven mainly
by locating print materials found in the library; we need to persuade
our teaching colleagues that when we propose to help students use the
library we aren't going to misrepresent to students what research is
Finding a focus is a major and critical phase in
undergraduate research. Unlike
expert researchers, students don't know enough about a field to see its
holes; they can't latch on to interesting issues without first
reviewing the literature to discover which questions are worth
pursuing. The methods librarians frequently recommend to students for
"narrowing" a topic, however, don't reveal interesting questions.
Narrowing by the mechanical means of adding geographical or
chronological constraints, or by looking at Library of Congress Subject
Headings, will indeed limit a topic--but in ways that are concrete,
settled, defined. These methods fail to identify interesting frontier
areas for research.
We need to develop strategies
that help students become familiar with a topic quickly, and that give
them some tactics for seeing the gaps, the places where questions lurk.
Otherwise the message we send is that research is a question of
mechanically limiting and reporting on a topic that has already been
thoroughly defined and explored by others.
need to forewarn them that developing a focus takes time and is a
creative and somewhat intuitive process. Students tend to view this
part of research as frightening and unproductive.(n12) They often feel
that they are spinning wheels or not approaching the problem correctly.
We can help reassure them that their feelings are normal and that this
phase of research is a necessary and important part of the whole. The
tool-based approach that librarians frequently present as a "logical
and systematic" process of research may well convince the student who
is having difficulty in the focus phase that browsing and scanning are
illogical and unsystematic and therefore wrong. Our tool-intensive
techniques, introduced in library school bibliography classes and
reenforced at the reference desk, work better for finding answers than
for identifying questions.
The "overview" needed to get started is rarely found
in a reference book.
It is significant that students in this study preferred to begin their
research by consulting their instructor rather than a librarian, even
when their questions were primarily bibliographic in nature: What's
being written about my topic? What are the most important studies? Who
are the authorities? They did not consult first with a librarian,
perhaps feeling 'that a subject specialist would be more likely to
connect them with other specialists than a librarian would, and would
provide more "inside information" than a reference tool would.
two of the students interviewed began research with a reference book.
One of these looked up her topic in an encyclopedia because she was
synthesizing information to prepare a lesson plan for a high school
French class. The other student wanted to compare the ways two
different fields defined a word, so she started with specialized
dictionaries. None of the other students found reference books helpful
as a first step--though many of them used them later in the process to
fill gaps in their information. Their topics were too diffuse, too new,
or too big to start with a specialized encyclopedia, and in most cases
they had as much information from theft textbooks or lectures as they
would find in a reference source.
by and large, are good for locating accepted knowledge from the fields,
as places to get quick facts, and as places to get overviews of topics
tangential to research; they are less successful at illuminating those
interesting gray areas that are the best place to develop a research
project. We need to reexamine the use of reference books as step
one--finding an overview of a topic--and instead study the process
researchers go through when focusing on a question, to learn ways to
make that part of the research process more rewarding and less
frustrating for students.
Finding tools are not always the best route to good
Our search strategies quite often describe the information-seeking
process as one in which tools--reference works, bibliographies,
catalogs, indexes--are used successively and systematically to locate
information, with the implication that most of the information used in
research is located through finding tools. In fact, students (and other
researchers) find the most direct and efficient route to sources
through the citation network. The students interviewed used finding
tools, browsing, and the citation network all to good purpose. They
used finding tools chiefly as a method of browsing the field in the
first phase of research, but relied more on citations in the later
phase, once the research question was thoroughly defined. If students
find much of their material through the citation network and through
serendipitous browsing of shelves, we should point those out as factors
in the search strategy rather than emphasizing the use of privilege
bibliographic tools as the correct way to locate information.
Generating an idea, gathering information, and
writing are parts of a single process.
The students interviewed did not begin with choosing a topic, go on to
seek information, and end up by composing a paper. These students
described a much more integrated process. None of them came into the
library with a chosen topic; the topic, or their particular angle on
their topic, developed as their research progressed. Writing, too, was
something they did throughout their research, not merely at the end of
the information-gathering phase. Relevant questions to ask ourselves
are: How much do we integrate "search strategies" into a larger picture
of research? Should we connect the information search with the other
simultaneous parts of the research process? Should we help prepare
students for research, not merely for search?
it falls to librarians to prepare students with the necessary skills to
use the library--and to the instructor to train the student to do
research--we must put the search skills into context and connect them
accurately with other aspects of research to make them useful to the
students we teach. It does not take a lot of class time to forge those
connections, and it makes the details of searching for information more
meaningful for students when seen in the larger context of research.
We need to know more about the research process.
Further work needs to be done if we are to accurately construct a map
for our students to use in negotiating a research project. When we tell
students the steps they should take, we are describing a process we
know little about. (Our approach could be likened to that of the
experts in Hilaire Belloc's Microbe: "Oh! Let us never never doubt what
nobody is sure about!") The following questions are particularly
We will, no doubt,
uncover more questions as we examine the research process of
undergraduates. But if we are to represent the process in a way that
accurately mirrors the circularity, the uncertainty, and the creativity
involved in research, we need to reexamine our tool-based, "systematic"
search model--and develop a new model that better addresses the special
needs of undergraduate researchers.
Tell me about your project. What was it about?
About your idea for the project--
How did you settle on this particular focus?
Was there a moment when the focus clicked for you, when you
knew what the focus would be, or did it gradually evolve?
you get a question in mind first and then look for answers, or did the
problem and its solution occur to you at the same time as an idea to
What factors played the most important role in developing your
theme? People? Things you read? Previous research?
draw a time line or chronology of the project so we can talk about
things you did in sequence. I'm interested in steps you took that
didn't work out, as well as in the things that did. How did you get
started? Then what? When and how did your focus change in the course of
the work? How did you wrap up the project?
Can you identify any pivotal points in the project, times when
you made a choice or when your research took a sudden turn?
What were the most productive parts of your research? The
parts that didn't go so well? Why?
Let's look at your list of sources. How did you find the
sources you listed here?
How do you like using the computerized catalog?
Did you use particular indexes? Were they helpful?
How did you decide which sources were good for this project?
What criteria did you use for choosing sources?
Did the teacher make her or his criteria explicit?
Are the criteria you used for choosing sources for this
project different from those for other kinds of research you have done?
Did you come across sources you disagreed with or two sources
that contradicted each other? How did you handle that?
Which of these sources played the most important role in your
research? In what specific ways did they make a contribution?
7. When did you discover these sources? Place them on the
Based on your research for this project, did you begin to see different
schools of thought or different factions among the writers whose work
Writing and Research
When on the timeline did you begin to write your paper?
Did you do any writing before actually starting the paper?
What kind of writing?
did you use the sources as you wrote the paper? Did you read through
them all and mark relevant passages first or did you look for evidence
as you wrote?
As you wrote, did you ever see the
need to return to the library (even if you didn't because of lack of
time) to find responses to questions that emerged in the course of
writing up the paper?
(n1) Stephen K. Stoan, "Research and Library Skills: An
Analysis and Interpretation," College & Research
Libraries 45 (March 1984): 99-109.
There are many published discussions of search strategies. Anne K.
Beaubien et al. define it as "the ordered arrangement of types of
finding tools appropriate for the collection of material on a
particular analyzed topic," in Learning the Library: Concepts
and Methods for Effective Bibliographic Instruction (New
York: Bowker, 1982), p. 92.
(n3) Stoan, "Research and Library Skills," p. 106.
(n4) Richard Feinberg and Christine King, "Short-Term Library
Skill Competencies: Arguing for the Achievable," College
& Research Libraries 49 (January 1988): 24-28.
(n5) Tom Eadie, "Immodest Proposals: Library Instruction for
Students Does Not Work," Library Journal 115
(October 15,1990): 42-45.
(n6) Ibid., p. 45.
(n8) Ibid., p. 42.
(n9) Constance A. Mellon, "Process Not Product in
Course-Integrated Instruction: A Generic Model of Library Research," College
& Research Libraries
45 (November 1984): 471-478; and Carol Collier Kuhlthau, "Developing a
Model of the Library Search Process: Cognitive and Affective Aspects,"
RQ 28 (Winter 1988): 232242.
(n10) Janet Emig, The Composing Processes of Twelfth
Graders (Urbana, IL: National Council of Teachers of English,
(n11) Stoan, "Research and Library Skills," p. 103.
(n12) Kuhlthau's study bears out the high level of anxiety
students feel during the topic formulation stage of research.
(n13) Mina P. Shaughnessy studied the problems experienced by
basic writers in her book Errors and Expectations: A Guide
for the Teacher of Basic Writing
(New York: Oxford, 1977), and makes the case that their errors aren't
due to stupidity or lack of application, but rather to unfamiliar and
misunderstood expectations. A similar study of errors made by library
users would be invaluable.
This article, published in Journal of Academic Librarianship, Vol 18, No 3, 1992, 163 – 169, is posted with permission from Elsevier. Elsevier wishes to note that single copies of the article can be downloaded and printed only for the reader’s personal research and study.