About 30 years ago we began to publish in Current Contents the series called �This week's Citation Classic�.  Over the next 15 years, we asked thousands of authors to write commentaries on these highly cited papers (http://www.citationclassics.org/). So I was surprised to be asked by an international journal of epidemiology to write a commentary for my 1955 paper in Science.¹  As a confirmed citationist, I must point out that it is not my most cited work. It is my 1972 paper in Science,² on using citation analysis to evaluate journals, which has attracted much more attention, although in my opinion the 1955 paper is far more significant.  In that sense, I am like many other authors who feel that their most-cited work is not necessarily their best. My most-cited work is in fact my 1979 book Citation Indexing.³

Tracing the genealogy of citations to this 1955 paper it reveals the evolution of the concept of citation indexing -- from a system for information retrieval to a tool for research evaluation. In a paper that I had prepared at the request of the then editor of Science in 1995, I suggested that the tail was now wagging the dog.⁴   This is the theme of my forthcoming Keynote Address in Dalian.

In the first few decades after the appearance of this 1955 paper, and its 1964 successor⁵, most of the citing papers concerned the pros and cons of citation indexing for information retrieval.  In those days librarians and others were preoccupied  with controlled vocabulary-based indexing. So we created the Permuterm Subject Index as a natural language supplement to the Citation Index. Henry Small much later would formalize the role of citations as concept symbols.⁶

An early portent of the use of SCI for evaluating science was the 1967 paper by Margolis.⁷  By that time Irving Sher and I had already done the simplistic exercise of sorting the Science Citation Index to produce a list of the 50 most cited authors.  About one-third of these proved to be Nobel Prize winners and almost all were authors �of Nobel Class�.⁸

When the 1955 paper was published there were no computers. Punched-card methods were considered revolutionary. Even 10 years later, when we launched SCI, punched cards were used as input to the first primitive IBM computers to produce the printed SCI.

In those days, Vannevar Bush's concept of Memex was as close as we came to thinking about the idea of an internet.⁹  But the linking properties of citations were fully recognized and given formal descriptions by my half-brother Ralph Garner¹⁰ and Derek Price.¹¹ The idea of mapping science based on the linking properties of citations was well understood and used to explore the historiography of DNA.¹² Early on a small group of people saw in the SCI its significant potential for bibliometric evaluations. It would be tempting to outline the various significant papers and reports that have eventually made the SCI a standard tool in the hands of science policy analysts and others interested in evaluation, including those who like to play parlour games predicting Nobel Prizes. However, the SCI is now not only considered essential in libraries and elsewhere but also sufficiently popular to engender competition from Google Scholar  and others.  Indeed it should be noted that citation linking is at the heart of Google's success as a search engine which is based on the page ranking process derived originally from JCR.

Reading my 1955 paper once again reminds me of the inspiration that the concept had from my early interest in encyclopaedism.  In 1970, Professor Manfred Kochen (University of Michigan) commented on its role in the worldwide encyclopaedic movement.¹³ Today the Internet has enabled the development of Wikipedia and other grand schemes that will make the H.G. Wells dream of a World Brain a reality.  I have sometimes called this Bibliographic Nirvana.

The relatively low memory capacity of computers in the early days would prevent their application for these uses for three or more decades. Since then the network properties of citation indexes have been explored by numerous investigators. These were pioneered by Derek deSola Price in his 1965 network¹¹ paper. It appeared shortly after my 1964 paper in Science⁵  which described the SCI not only as a new dimension in indexing but pointed to its use in science evaluation. It is easy to forget today that even ten years after  the first printed SCI annual was published, libraries hotly debated whether to purchase it to supplement or even replace a combination of traditional indexing services. Eventually the basic conservatism of scientists and librarians was overcome. This evolution paralleled the growth in computer memory capacity -- from the 16K memory of the IBM 1401 computer we used in those days, to the gigabyte capacity we take for granted today.   It was even more accepted when ISI added author abstracts to the database.  When that occurred, many libraries no longer felt the need to retain the traditional abstracting services.

While the Web of Science is now routinely used in industry for alerting purposes, one of my greatest disappointments has been the failure of  most scholars to use it as an alerting tool, i.e. for selective dissemination of information or SDI.  Today SDI is performed by weekly or daily citation alerts, but the first such service, the Automatic Subject Citation Alert (ASCA),¹⁴ was started in 1965, a year after we started SCI. It is still difficult for most users to develop citation consciousness which is another way of saying they resist the preparation of search profiles including cited references as well as keywords.  I hope this brief history will provoke questions which I would be very happy to answer.

Thank you.

1.     Garfield E. "Citation indexes for science: a new dimension in documentation through association of ideas" Science 1955;122:108-11.
Available at: http://garfield.library.upenn.edu/papers/science_v122v3159p108y1955.html (Reprinted Int J Epidemiol 2006;35:1123-27.)

2.     Garfield E. "Citation analysis as a tool in journal evaluation" Science 1972;178:471-479.
Reprinted in Current Contents, 1973; Reprinted in Essays of an Information Scientist, Volume 1, pp. 528-44. Philadelphia: ISI Press, 1977.
http://garfield.library.upenn.edu/essays/V1p527y1962-73.pdf

3.     Garfield E. "Citation Indexing: Its Theory and Application in Science, Technology, and Humanities" Philadelphia: ISI Press, 1977, p. 79.
http://garfield.library.upenn.edu/ci/title.pdf

4.     Garfield E. "From citation indexes to informetrics: Is the tail wagging the dog?" Libri 1998;48:67-80.
http://garfield.library.upenn.edu/papers/libriv48(2)p67-80y1998.pdf

5.     Garfield E. "Science Citation Index : a new dimension in indexing"  Science  1964;144:649-54.
http://garfield.library.upenn.edu/essays/v7p525y1984.pdf

6.     Small HG. "Cited documents as concept symbols" Soc Stud Sci 1978;8:327-340.
http://garfield.library.upenn.edu/small/hsmallsocstudsciv8y1978.pdf

7. Margolis J. "Citation indexing and evaluation of scientific papers"  Science 1967;155:1213
http://www.sciencemag.org/cgi/content/abstract/155/3767/1213

8.     Garfield E. "Citation Indexing for studying science"  Nature 1977;227:669-671.
Reprinted in Current Contents, 1970; Essays of an Information Scientist; Volume 1, pp. 132-38. Philadelphia: ISI Press, 1970.
http://garfield.library.upenn.edu/papers/naturev227p669y1970.pdf

9.     Bush V. "As We May Think"  Atlantic Monthly 1945;176:101-08.
Available at: http://www.theatlantic.com/doc/194507/bush

10.     Garner R. "A Computer Oriented, Graph Theoretic Analysis of Citation Index Structures"  Philadelphia: Drexel University Press, 1967.
http://garfield.library.upenn.edu/rgarner.pdf

11.     Price DJD. "Networks of scientific papers: the pattern of bibliographic references indicates the nature of the scientific research front" Science 1965;149:510-15.
http://garfield.library.upenn.edu/papers/pricenetworks1965.pdf

12.     Garfield E, Sher IH, Torpie RJ. "The Use of Citation Data in Writing the History of Science"  Philadelphia: Institute for Scientific Information, 1964, p. 75. http://garfield.library.upenn.edu/papers/useofcitdatawritinghistofsci.pdf

13.     Kochen M. "WISE: world information synthesis and encyclopedia"  J Document 1972;28:322-343.

14.     Garfield E, Sher IH. "ISI's experiences with ASCA: a selective dissemination system"  J Chem Document 1967;7:147-53. Reprinted in Essays of an Information Scientist, Volume 6, p. 533 Philadelphia: ISI Press, 1984.
http://garfield.library.upenn.edu/essays/v6p533y1983.pdf