Keywords
citations - quotations - reference management software - references
Introduction
With ongoing advancements in science and technology, there is a tremendous increase
in the volume and rate of academic publications. In medical literature, citations
play a fundamental role in shaping the integrity, credibility, and progress of scientific
knowledge. Referring to and citing existing literature are indispensable components
of academic writing. While “citations” refer to the source of borrowed information
(definitions, classifications, results, figures, etc.), “references” enlist the sources
of information cited in the body of the text. This article reviews the importance,
various types, and methods of citations in academic publications.
Importance of Citing References
Importance of Citing References
Citing references in scientific publications is essential to maintain integrity and
promote the visibility of research. Citations ensure that due credit is given to the
original ideas and outcomes of other researchers.[1] They provide context and background information on the preexisting knowledge in
a particular field. This allows readers to trace the origins of methods and interpretations
used in a study, which guides future research.[2] When credible sources and preexisting data on a topic are cited, the reader is assured
that the author has conducted a thorough literature review, enhancing their reputation.
Citations are one of the most fool-proof methods to avoid plagiarism and uphold ethical
integrity.[3] Further, they foster an academic environment by linking researchers with similar
interests and promoting collaboration within the academic community. In summary, citations
ensure transparency, acknowledge contributions and support the advancement of knowledge
within a particular field of study. Despite being an important part of a manuscript,
misquotations and bibliography errors are common, with their prevalence ranging from
50 to 70%.[4]
High-quality citations refer to data from a relevant, original cited source. “Empty
citations,” which simply refer to other studies supporting a claim and do not directly
report the claim, must be avoided. They misrepresent information without citing the
original source, rather, they cite a more recent publication that cites the native
source. High-quality citations also validate results by referring to individual, empirical
studies, without misrepresenting their content. Articles from top journals should
not always be considered as the ultimate truth, rather, they should be analyzed in
an unbiased manner. Also, the publications contradicting the outcome of a study should
be pointed out neutrally and should not be argued with.[5]
Parts of Citations
A citation has three parts: (1) Quotation, which quotes or provides a summary of others' work, (2) in-text reference, which is a brief address to the source, and (3) reference list, which mentions the name of authors, source, and date of publication.
Quotation and In-Text Referencing
Information from other sources can be mentioned as direct quoting, paraphrasing, or
providing a summary.[6] When quoting directly, the information is presented in the same words used in the
source, placed within quotation marks. It is used when the original words, rather
than paraphrasing, add clarity to a statement. Direct quotations are also preferred
over paraphrasing when mentioning well-known facts or historical data.[7]
When paraphrasing, the author analyzes previously published information and expresses
it in their own words. Paraphrasing and summarizing data need skill and knowledge,
and do not mean mere usage of synonyms or “patch-writing” sentences.[8] While paraphrasing it should be ensured that the original statements are accurately
presented, without misunderstanding.[6]
When summarizing, the author provides a brief report of published information in a
neutral, affiliating, or distancing tone, depending on their stance.[2] Appropriate verbs are used to express the author's opinion on the matter. For a
neutral approach, verbs such as “describe,” “suggest,” “state,” etc. are used. Using
the present tense in the verb implies that the source is recent and relevant, while
the past tense indicates that the source is older.[9] Verbs affiliating with the cited literature include “recognize,” “identify,” “reveal,”
etc., and verbs distancing from the literature include “assume,” “claim,” “hope,”
etc.
Quotations in the text are followed by in-text citations referring to the source of
information. These briefly address the source in the text and may be presented in
any of the three major systems: “citation-sequence,” “citation-name,” and “name-year”
systems. In the “citation-sequence” system, the list of references is numbered in
the order of appearance in the text.[10] In the “citation-name” system, the reference list is arranged according to the alphabetical
order of the first author names, irrespective of their sequence of appearance in the
text.[11] In the “name-year” system, the reference list is arranged first by the surname of
the author and then by the year of publication. In case there are two references by
the same author, chronological hierarchy is followed in the reference list, that is,
the latter follows the earlier publication. If the first author and publication year
are the same for two references, they are differentiated by alphabetical letters after
the year of publication (e.g., Author2023a followed by Author2023b).[12] The “citation-sequence” and the “citation-name” systems are also known as the Vancouver
and Harvard systems, respectively; these are the commonly used referencing systems
in biomedical literature.[9] These are explained later in the article.
Reference List
The reference list is located toward the end of the manuscript and has an entry corresponding
to every citation in the text. The exceptions are personal communications and unpublished
data, which are cited in the text, but not added in the reference list.[11]
[13] The recommended methods of citing various sources of reference, such as journal
articles, books, Web sites, etc. are given in [Table 1].
Table 1
Styles of citations with reference styles
Citation styles
|
In-text citation format
|
Reference style
|
Vancouver style
|
Numeric citation: [1] or (1) or superscript number: 1
|
Author(s). Title of the article. Journal name. Year;volume(issue):page numbers.
|
Harvard styles
|
Author(s) last name (year) or (author(s) last name, year)
|
Author(s). Year. Title of the article. Journal name, Volume(issue), pages.
|
Chicago style
|
(Author[s] last name year, page number)
|
Author(s). “Title of the Article.” Journal name, volume no. issue (year): pages
|
National Library of Medicine style
|
Superscript number: 1 or parenthetical number: (1)
|
Author(s). Title of the article. Journal name. Year month day;volume(issue)
|
American Psychological Association style
|
(Author(s) last name, year)
|
Author(s). (Year). Title of the article. Journal name, Volume(issue), pages.
|
American Medical Association style
|
Superscript number: 1
|
Author(s). Title of the article. Journal name. Year;volume(issue)
|
Modern Language Association style
|
(Author[s] last name page number)
|
Author(s). “Title of the Article.” Journal name, vol. Volume, no. issue, year, pp.
pages.
|
Turabian style
|
(Author[s] last name year, page number)
|
Author(s). “Title of the Article.” Journal name volume, no. issue (year): pages.
|
Institute of Electricals and Electronics Engineers style
|
|
Author(s). “Title of the Article,” journal name, vol. volume, no. issue, pp. pages,
year.
|
Styles of Citation
Various systems of citation and referencing are used in the literature, and the system
used depends on the scientific discipline and the preference of journal/publisher.
In medical literature, the Vancouver (citation-sequence) and Harvard (name-year) systems
are commonly used. In the footnote/endnote system, references are listed at the bottom
of the page, and they are cited as superscript numerical throughout the text.[13] Other systems which are less commonly used include the American Medical Association,
the Modern Language Association, the American Psychological Association, and the Chicago
Manual of Style. These citation styles are briefly outlined in [Table 1]. Since the Vancouver and Harvard systems are commonly used in medical literature,
only these are explained in detail in this article. A group of medical journal editors
informally met in 1978 in Vancouver, British Columbia, to formulate the guidelines
for manuscripts submitted to their journals.[14] Their consensus came to be known as the Vancouver style, and these were first published
in 1979. The Vancouver requirements were developed by the U.S. National Library of
Medicine. The Vancouver group has since expanded into the International Committee
of Medical Journal Editors and meets annually to update guidelines on “the Uniform
Requirements for Manuscripts Submitted to Biomedical Journals.”[15] The Vancouver style follows the author-number system; references are numbered consecutively
in the text using Arabic numerals in parentheses, and the reference list follows the
order of appearance of references in the text. Examples of using the Vancouver style
for various types of references are shown in [Table 2].
The Harvard system or “author-date” system is a less popular referencing style. It
was named by an English visitor impressed by the author-year citation system he encountered
in the library of Harvard University.[16] When following this system, the author's name and year of publication are given
in the body of the text, and the references are arranged alphabetically at the end
of the text. If there are up to three authors, their last names are mentioned in the
in-text reference. If there are four or more authors, the citation is abbreviated
with “et al” following the last name of the first author.[17] The Harvard system is sometimes criticized due to difficulties faced by the readers
while looking up for a reference since they are not arranged in the order of appearance.
Most journals specify the reference system to be used in submitted manuscripts. Some
journals provide detailed guidelines on how to format references according to their
preferred style, ensuring consistency and adherence to established standards. According
to the style, the format in which the citation is written and punctuated varies for
different kinds of scientific publications such as articles, books, newspapers, magazines,
and other electronic sources. The representation of various sources in the Vancouver
style is depicted in [Table 2].
Table 2
Methods of citing various publications in Vancouver style
Source
|
Vancouver style
|
Journal article
|
Author(s). Title of the article. Journal name. Year; volume(issue)page numbers.
|
Jordan LC, DeBaun MR, Donahue MJ. Advances in neuroimaging to improve care in sickle
cell disease. The Lancet Neurology. 2021 May 1;20(5):398–408.
|
Book
|
Author(s). Title of the Book. Edition. Place of publication: publisher; year.
|
Demaerel P. Recent Advances in Diagnostic Neuroradiology. Berlin, Heidelberg: Springer
Nature;2001.
|
Book chapter
|
Author(s) of the Chapter. Title of the Chapter. In: Editor(s), editors. Title of the
Book. Edition. Place of Publication: Publisher; Year:pages.
|
Krishna V., Sammartino F. and Rezai A.R. The Use of New Surgical Technologies for
Deep Brain Stimulation. Elsevier;2018:77–485.
|
Conference paper
|
Author(s). Title of the paper. In: Editor(s), editors. Title of the Conference; Date
of the Conference; Location. Place of Publication: Publisher; Year:pages.
|
Brown L, Thompson R. Innovations in Medical Imaging. In: Williams K, editor. Proceedings
of the International Conference on Medical Science; 2024 Aug 1–3; Paris. New York:
Springer; 2024:8–97.
|
Reference Management Software
Reference Management Software
Reference management software helps in collecting, storing, and organizing references.
They also enable in-text citations to be added in the text and automatically generate
a bibliography of references in the preferred style. Commonly used reference managers
include Zotero, Mendeley, EndNote, and RefWorks. These maybe web-based or can be installed
as an application. They allow downloading references as PDFs, screenshots, webpages,
etc. and organize them into the selected folder, which can be used multiple times,
as well as shared with other collaborating researchers. Reference managers also automatically
update the references and bibliography when citations are added to or removed from
the text.
The reference management software uses specific file formats for tagging information
of citations (RIS, BibTeX, EndNote, Medlars, and RefWorks) into the appropriate fields
(e.g., author, title, journal title). RIS (.ris) was developed by the Research Information
Systems and includes two letters, two spaces, and a hyphen indicating the citation
details as TY—“type of reference,” AU—“author,” PY—“publication year,” T1—“primary
title,” T2—“secondary title” (journal title), SP—start page,” EP—“end page,” VL—“volume,”
and IS—“issue”.
In the BibTeX format, the reference comprises three parts namely a case-insensitive
entry type (represented as @book/@article/@conference), a unique cite key (usually
the last name of the first author with the year of publication), and key-value pairs
containing the bibliographic information (such as title, author, publisher, address,
edition, year). Nonstandard field types such as DOI, ISSN number, ISBN number, and
web-page URLs are not supported by all reference management software.
It is important to consider various key factors while choosing a reference management
tool, including the features offered by the software. [Table 3] outlines the differences between the four commonly used software namely Zotero,
Mendley, EndNote, BibTeX, and RefWorks. It unfolds their basic features and their
availability and ability to integrate with different writing software.
Table 3
Comparison of various commercially available reference management software
Feature/software
|
Zotero
|
Mendeley
|
EndNote
|
RefWorks
|
BibTeX
|
Cost
|
Free (premium storage available)
|
Free (premium storage available)
|
Paid
|
Paid
|
Free
|
Availability
|
Windows, macOS, Linux, Web
|
Windows, macOS, Linux, Web
|
Windows, macOS
|
Web-based
|
Windows, macOS, Linux
|
File formats supported
|
RIS, BibTeX, EndNote
|
RIS, BibTeX, EndNote
|
RIS, EndNote, BibTeX
|
RIS, EndNote, RefWorks
|
BibTeX
|
Support for nonstandard fields
|
High (DOI, ISBN, URLs, custom fields)
|
Moderate (DOI, ISBN, URLs)
|
High (DOI, ISBN, URLs, custom fields)
|
Moderate (DOI, ISBN, URLs)
|
High (via LaTeX customizations)
|
PDF management
|
Yes
|
Yes
|
Yes
|
Yes
|
No
|
Annotation tools
|
Yes
|
Yes
|
Yes
|
Yes
|
No
|
Integration with word
|
Yes
|
Yes
|
Yes
|
Yes
|
No
|
Integration with LaTeX
|
Yes (with plugins)
|
Limited (via BibTeX export)
|
Yes (via BibTeX export)
|
No
|
Yes (native support)
|
Cloud sync
|
Yes
|
Yes
|
Yes
|
Yes
|
No (manual syncing)
|
Collaboration features
|
Yes (groups and sharing)
|
Yes (groups and sharing)
|
Yes (shared libraries)
|
Yes (shared projects)
|
Limited (via shared .bib files)
|
Import options
|
Manual, import from Web, PDF
|
Manual, import from Web, PDF
|
Manual, import from Web, PDF
|
Manual, import from Web, PDF
|
Manual (text editing or tools)
|
Export formats
|
RIS, BibTeX, EndNote, XML
|
RIS, BibTeX, EndNote, XML
|
RIS, BibTeX, EndNote, XML, CSV
|
RIS, EndNote, RefWorks
|
BibTeX
|
Customization and flexibility
|
High (via plugins)
|
Moderate
|
High
|
Moderate
|
High (through LaTeX and BibTeX options)
|
Drawbacks and Problems with Citations
Drawbacks and Problems with Citations
There is no denying that citations are crucial for maintaining academic integrity
and dissemination of knowledge. However, they come with their own set of challenges.
The most common issue is misquoting or mispresenting sources, which leads to the spread
of inaccurate information. Many bibliographic errors are found, such as incorrect
author names, titles, and publication details, which can undermine the credibility
of the work.[4] Moreover, the overuse of citations, particularly when referencing marginally related
work, can clutter a paper and detract from originality. Also, the complexity of managing
citations between multiple styles and formats can lead to inconsistencies while using
different tools or collaborating across disciplines.
Poor citation practices negatively impact the quality and integrity of research. Apart
from factual errors, other commonly encountered citation malpractices include quoting
incorrect citations, misinterpretation of results (intentional or unintentional),
unnecessary extrapolation of outcomes of cited work, preferentially citing irrelevant
works of colleagues, ignoring a more suitable reference, etc. Other issues such as
citation padding and self-citation have been described later. The pertinence of a
citation is one of the determinants of its validity. Citing impertinent references
is considered invalid. Some workers also argue that citations made in the introduction/review
of literature sections are impertinent, since if they were valid to the study, they
should be used in the methodology/results/discussion sections.[18]
Citation bias arises from selective citation of work supporting the results of a study while consciously
refraining from citing prior work contradicting the outcome.[19] As a result of it, the outcome of a study determines its chance of being cited,
resulting in a bias. For example, if a study comparing the outcomes between patients
treated with methods A and B finds method A to be superior, there are higher chances
that previous studies that also show the superiority of method A are cited in the
current study, and studies claiming method B to be superior are cited less frequently.
Various studies have demonstrated that authors tend to selectively cite studies with
positive outcomes, to enhance their results and make their study appealing to reviewers.[20]
[21] This leads to false polarization in a particular direction. Outcome reporting bias refers to selective reporting of certain findings within a publication. The probability
of a work being cited also depends on the journal it is published in. For example,
articles published in journals with higher readership and impact factors tend to have
a greater chance of being cited.[22] Further, in an attempt to satisfy the editor of the targeted journal, authors may
cite work published in that journal, even if irrelevant.
A meta-analysis on the citation rate and hit rate of studies on hip fracture trials
(internal fixation vs. arthroplasty) showed that the overall citation rate was 48%,
that is, only 48% of possibly citable relevant studies were actually cited. Further,
studies with a positive result (favoring arthroplasty) were highly cited.[23] Another analysis of citations in original reports and review articles in ecology
journals states that 22% of citations were inaccurate, that is, they misrepresented
the cited authors' findings and 15% of citations gave unfair credit to the review
authors for others' ideas.[24]
[25] Such misbehaviors could lead to redundancy in publication and misguidance of readers.
Antiplagiarism software primarily highlights instances where the text significantly
resembles previously published work. When using direct quotations—that is, the exact
words from a source—these should always be enclosed in quotation marks and followed
by a suitable citation. For example: “One of the main challenges of scientific writing is to pack vast and complex information
into clear and well-structured texts. It is a skill that requires not only knowledge
of the scientific field but also practice in writing” (Rogers, S.M., 2014).[7] When following this citation style, both readers and plagiarism detection software
can easily recognize that the words and ideas belong to the cited author.
However, it is important to ensure that quotations are sparingly used and that proper
citation methods are followed according to journal-specific guidelines. Paraphrasing
with correct citation is often recommended to illustrate the author's comprehension,
rather than copying verbatim from the sources.[26]
Editor/Reviewer and Citation Checking
Editor/Reviewer and Citation Checking
Together, editors and reviewers are the gatekeepers of academic and scientific writing
as they ensure that only high-quality, reliable, and ethical research is published.
In the context of citations and referencing, editors and reviewers have critical responsibilities
to ensure that the citations which are used in the manuscript are accurate, relevant,
and properly formatted. They ensure the adherence of the manuscript to the journal's
referencing guidelines. They also ensure that citations and referencing are done appropriately
to support claims.
Citation padding refers to the use of excessive citations that are not directly relevant, while self-citation refers to quoting an author's previous work in their current work. Editors and reviewers
may perform random checks on citations to ensure that referred works are accurately
represented, to verify the originality of the content, to highlight ethical considerations,
and to address any instance of plagiarism.
Despite blinded reviewers having no access to the identity of the author, certain
patterns in the manuscript may indicate self-citation, for example, if a manuscript
carries a disproportionately high number of citations to a single researcher or research
group. In some cases, citations of articles from smaller or less specialized journals
may be a red flag as they may indicate an author citing their own lesser-cited work
to increase their perceived impact. The editor can however determine if self-citations
are excessive or unjustified based on available metadata. It is acceptable to incorporate
a reasonable amount of self-citation, particularly when it directly contributes to
the topic. It can be dangerous to cite or rely on prior research if excessive or unwarranted
self-citation is used.[27] A reviewer or editor may flag excessive self-referencing as a threat to the objectivity
of the research.[28]
Ultimately, the editors and reviewers provide feedback to the authors and guide them
to correct the issues. This includes suggesting the removal of irrelevant citations,
the addition of missing ones, or correct formatting of the reference list.
Although less common, citation and referencing errors may result in the outright rejection
of manuscripts. Studies indicate that errors in referencing can be a factor in the
rejection of manuscripts, with citation-related problems being a contributing reason
in ∼10 to 15% of rejections.[29]
Artificial Intelligence–Driven Citation Checkers
Artificial Intelligence–Driven Citation Checkers
Ongoing recent developments in the realm of artificial intelligence (AI) have led
to the development of AI-driven citation checkers. Commonly used online citation-checking
tools include Trinka (https://www.trinka.ai/), Scribbr (https://www.scribbr.com/), and Scite Assistant (https://scite.ai/). These tools use AI to proofread the uploaded content and quickly provide corrections
for grammar and citation errors, when common citation styles are used. In addition,
they are also trained to detect AI-generated content, generated using large language
models (LLMs) such as ChatGPT, GPT-4, Bard, and Bing Chat. These tools instantly scan
the uploaded content and highlight the LLM-created content, with their percentage.
Scientometrics and Citations
Scientometrics and Citations
Measurement and analysis of scientific publications are often done using bibliometric
methods. Impact factor and H index are important parameters to assess scientific publications.
The impact factor measures citations of a published article in a journal. A journal's
impact factor of a particular year is the average number of citations received per
article in that journal, published in the preceding 2 years.[30] A journal with an impact factor of 7 in 2023 means that there was an average of
seven citations of articles published in that journal during the years 2021 and 2022.
It is calculated as a ratio of the number of cited articles published in the previous
2 years to the total number of articles published during those 2 years.
H index measures the impact and productivity of scientific publications, based on
the most cited papers and the number of citations received in other articles. It can
also be used as a measure of impact of a researcher based on citations received by
that researcher's publications. For example, if a researcher has an H index of 7,
it means that 7 of their publications have at least 7 citations each, and the rest
of the papers have not more than 7 citations in other journals. Hence, the H index
not only reflects the number of publications done by a researcher but also the number
of citations for a publication. It helps in comparison of researchers in the same
field and may not be comparable across different specialties.[31]
Other journal metrics include Eigenfactor Score, CiteScore, and SCImago Journal Rank
(SJR). The Eigenfactor Score of a journal measures the number of times articles published
in that journal in the past 5 years have been cited in the Thomson Scientific Journal
Citation Reports year. Similar to impact factor, it is a ratio of the number of citations
to the number of articles. However, it has the added advantage of eliminating self-citations
by removing citations from the same journal. It also weighs each reference with a
stochastic measure of the amount of time spent reading the journal.[32] CiteScore is a citation metric launched by Elsevier. It is calculated for the journals
indexed in Scopus. Unlike the impact factor, CiteScore uses a 3-year period.[33] SJR also ranks journals indexed in Scopus database. SJR refers to the frequency
with which publications in a journal were cited in other journals in the 3 preceding
years (compared with 2 years for impact factor). However, SJR weighs incoming citations
to a journal by the SJR of the citing journal, ensuring that citations from journals
with higher SJR are given a higher rank than citations from a source with lower SJR.
A journal with SJR >1 has above-average citation potential.[34]
[35]
Future Directions in Citation Practices
Future Directions in Citation Practices
With the transition of scholarly correspondence from offline publications to online
content, citations commonly include hyperlinks to web-based content. However, the
linked content maybe dynamic, lack stability, and may change, over time. This results
in “reference rot,” which arises from “link rot” (when the linked page is not found,
displayed as error 404) or “content drift” (when the linked content has changed/drifted
over time). A few strategies have been described, to avoid reference rot.[36] Authors can create snapshots of web pages linked to citations in the manuscript
preparation stage. This ensures that the metadata and the date and time of snapshot
are recorded.[37] However, reference rot might have already begun before the article was published
and some web content in the references might have changed/disappeared by the late
editorial stage. So, it is prudent that the author and editor check and ensure that
appropriate evidence is cited. Also, by incorporating saved copies of sources into
their web-based citations, researchers can preserve the integrity of their citations.
Conclusion
Citations play a pivotal role in academic publications by ensuring the credibility,
traceability, and academic integrity of research. They allow researchers to build
upon existing knowledge, facilitate peer review, and guide readers to sources for
further exploration. Proper citation practices not only honor the contributions of
previous researchers but also enhance the reproducibility and reliability of scientific
findings. As the foundation of scholarly communication, citations uphold the quality
and advancement of science, making them indispensable in the pursuit of knowledge
and innovation. Properly citing references in scientific publications is a critical
skill, and the current article reviews the basics of citations and references.