A citation index keeps track of which articles in scientific journals cite which other articles. The most well-known and widely-used citation index is the Web of Science published by the Institute for Scientific Information (ISI).

The best initial source of information is the book "Citation Indexing" published in 1979 by John Wiley and reprinted in 1983 by ISI. Eugene Garfield has posted the full text at [1] as well as hundreds of papers by him and other authors. There is a vast literature on citation analysis, sometimes called scientometrics, a term that was invented by V. V. Nalimov. The field blossomed with the advent of the Science Citation Index, which now covers over fifty years of source literature. The leading journals of the field are Scientometrics and the Journal of the American Society of Information Science and Technology. ASIST also hosts a listserv called SIGMETRICS at ASIST.

While the SCI was originally designed for information retrieval purposes and is used daily for that function, it has been increasingly used for bibliometric and other studies involving research evaluation.

In a classic 1965 paper, Derek J. de Solla Price described the inherent linking characteristic of the SCI as "Networks of Scientific Papers". [2] . The links between citing and cited papers became dynamic when the SCI in print medium was changed to online. The Social Sciences Cition Index became of the first databases to be mounted on Dialog in 1972. With the advent of the CD-ROM edition linking became even easier and enabled the use of bibliographic coupling (M. M. Kessler) for finding related records. In 1973 Henry Small published his classic work on Co-Citation analysis which became a self-organizing classification system that led to document clustering experiments and eventually an Atlas of Science later called Research Reviews. An early offshoot of the SCI in 1965 was the launch of the first commercial system of selective dissemination of information called Automatic Subject Citation Alert. This system continues to the present in electronic form at the ISI Personal Alert. However, other systems like Dialog among others also adopted the idea of SDI by providing weekly updates of literatue searches based on using user profiles. In the case of SCI/SSCI profiles contained not only traditional search terms (natural language) but also cited reference or cited author terms. Thus, a user could be alerted to any new works which cited the author, paper or book in question. The same token using journal names a selective, customized contents page service could also be provided.

The inherent topological nature of the worldwide citation network which is an inherent property of the scientific literature was described by Ralph Garner at Drexel University in 1965. The use of citation counts to rank journals was a technique used in the early part of the nineteenth century but the measurement of these links to rank authors and papers was pioneered by Garfield at the Institute for Scientific Information. In a primordial paper of 1965 he and Irving Sher showed the correlation between citation frequency and eminence in demonstrating that Nobel Prize winners published five times the average number of papers while their work was cited 30 to 50 times the average. In a long series of essays on the Nobel and other prizes Garfield reported this phenomenon.

In an early study in 1964 of the use of Citation Analysis in writing the history of DNA, Garfield and Sher demonstrated the potential for generating historiographs, topological maps of the most important steps in the history of scientific topics. This work was later automated by Garfield, Pudovkin and Istomin and led to the creation of the HistCite software.

External links

• Official website ISI
• Google Scholar Scientific search engine provided by Google, makes heavy use of citation statistics.