Using Citation Indexes
What Are Citation Indexes?
Citation indexes track references that authors put in the bibliographies of published papers. They provide a way to search for and analyze the literature in a way not possible through simple keyword/topical searching. It also enables users to gather data on the "impact" of journals, as well as assessing particular areas of research activity and publication. This field is called bibliometrics.
Citation indexing began in the 1950s, and has long been dominated by the former Institute for Scientific Information (ISI, now owned by Thomson Reuters). Thomson publishes three citation indexes: Science Citation Index (SCI), Social Sciences Citation Index (SSCI), and Arts & Humanities Citation Index (AHCI), plus two Conference Proceedings Citation Indexes (CPCI). This page focuses on the use of SCI in the "hard" sciences, which have the longest track record in citation studies. SCI covers more than 6,000 journals across all science and engineering disciplines.
UT-Austin users can access the citation indexes back to 1965, plus the conference proceedings citation index back to 1990, via the Web of Science system.
What Can I Do with Citation Indexes?
- 1. Find papers that cite earlier papers.
- Citation indexing is a way to look forward in the literature from the starting point of a particular paper or group of papers. This is a different and complementary approach to ordinary word-based literature searching, which looks backward in the literature from the present time.
For example, if you have an excellent paper on a particular topic that was published in 1992, you can use Science Citation Index (via Web of Science) to find papers published after 1992 that cited that paper. Citation implies a direct subject relationship between the papers. So, by searching for later papers citing your known paper, you can find more documents on the same or similar topic without using any keywords or subject terms.
- 2. Find out how many times my papers have been cited. Determine my h-index.
- This is a lot more complicated than it sounds!
- 3. Determine which are the "best" journals in my field.
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Citation data have long been used to rank journals within particular subject areas, usually based on the ISI Impact Factor. The impact factor is a numerical ratio of the total number of citations a journal receives in Web of Science Source Journals in one year to the total number of "citable" articles it published in the previous two years. It is useful to see how journals perform in relation to others in the same subject area. It is not useful in comparing journals across subject areas, and the number taken out of this context is essentially meaningless.
For example, Journal A has an impact factor of 4.327, and Journal B has an impact factor of 1.045. Is Journal A "better" than Journal B? You could conceivably make that argument, if you first accept the notion that quality equates with citedness, AND if journals A and B are both in the same field. But if A is in Biochemistry, and B is in Clinical Pharmacy, no such judgment can be made, as citation behavior varies considerably from field to field.
Impact factor can also vary based on the number and types of articles a journal publishes. Review articles tend to be more heavily cited than full papers or communications, so journals and annuals that publish mostly reviews will often have high impact factors. Journals that publish only a few articles in a given year may also have disproportionately high impact factors. Similarly, one very highly cited paper can skew a journal's impact factor.
Impact factors for journals covered by ISI are published annually in Journal Citation Reports. All WOS Source Journals are ranked within one or more relevant subject categories, such as CHEMISTRY, ORGANIC or SPECTROSCOPY. You can also compile customized lists. JCR also contains data on historical trends, immediacy index, cited half-life, etc.
While Impact Factors are useful within certain limits, they are subject to manipulation. Lack of transparency and reproducibility has been cited as an ongoing problem (see readings below). Nor does a journal's IF relate in any way to the impact or quality of an individual author or paper. As a result, the use of journal impact factors in personnel and funding decisions is strongly discouraged.
SJR SCImago is different journal ranking system based on citation data from Elsevier's Scopus database. Another project called Eigenfactor uses network theory to group journals and their citations and evaluate their relative importance.
- 4. Verify old and obscure references.
- Sometimes you'll run across a mysterious reference, and you won't be able to determine what it's referring to. By searching that reference as a "cited reference" in Web of Science, you may find other, more complete citations that might solve the mystery. It doesn't matter how old the mystery item is -- if someone has cited it it will show up in the Citation Index.
Further Reading
- Adams, David. "The Counting house." Nature 415, Feb. 14 2002, 726-32.
- Altbach, Philip G. "The Tyranny of Citations." Inside Higher Ed, May 8, 2006.
- Bauer, Kathleen; Bakkalbasi, Nisa. "An examination of citation counts in a new scholarly communication environment." D-Lib Magazine, 11(9) Sept. 2005.
(A case study comparing citation counts in Web of Science, Google Scholar, and Elsevier's Scopus products.)
- Garfield, Eugene. "Dispelling a few common myths about journal citation impacts." The Scientist, 11(3) 1997.
- Harzing, A. Reflections on the h-index.
- Hirsch J.E. (2006) "An index to quantify an individual's scientific research output." Proceedings of the National Academy of Sciences 102: 16569-16572.
- "The Impact Factor Game." PLoS Medicine 3(6) 2006, e291.
- International Mathematical Union. Joint Committee on Quantitative Assessment of Research. "Citation Statistics." Report, June 11, 2008.
- Jasco, Peter. Google Scholar's ghost authors. Library Journal, Nov. 1, 2009.
- Meyer, V. "The h-index: help or hype?" Chimia, 63(1-2) 2009, 66-68.
- Molinié, A.; Bodenhausen, G. "Bibliometrics as weapons of mass citation." Chimia, 64(1-2) 2010, 78-89.
- Monastersky, Richard. "The number that's devouring science." Chronicle of Higher Education, Oct. 14, 2005.
- Nature Special Issue: Science Metrics. June 16, 2010.
- "Not-so-deep impact: research assessment rests too heavily on the inflated status of the impact factor." Nature. 435, 2005, 1003-4.
- Neff, Bryan D.; Olden, Julian D. (2010). "Not So Fast: Inflation in Impact Factors Contributes to Apparent Improvements in Journal Quality." BioScience 60(6):455-459.
- Reedijk, Jan. "Sense and nonsense of science citation analyses." New Journal of Chemistry, 1998, 767-70.
- Rossner, Mike; Van Epps, Heather; Hill, Emma. "Show me the data." Journal of Cell Biology, 179 (6) 2007, 1091-1092.
- Rovner, Sophie L. "The Import of impact." Chemical & Engineering News 86(21), May 26, 2008, 39-42.
- Seglen, Per O. "Why the impact factor of journals should not be used for evaluating research." BMJ 314 (7079) 1997, 498-502.
- Stringer MJ, Sales-Pardo M, Nunes Amaral LA (2008) "Effectiveness of Journal Ranking Schemes as a Tool for Locating Information." PLoS ONE 3(2): e1683.
- The use and misuse of bibliometric indices in evaluating scholarly performance ESEP, Ethics in Science and Environmental Politics, 8(1) 2008.
- Walter, G. et al. "Counting on citations: a flawed way to measure quality." Medical Journal of Australia, 178(6) 2003, 280-81.
ISI publishes an online newsletter,
In Cites, that contains articles and reports about current citation trends, "hot papers," and lists of highly cited scientists. ISI also maintains a site called
ISI Highlycited.com that lists highly cited scientists in various fields, along with their biographies and publication lists.
