Citation index
Encyclopedia
A citation index is a kind of bibliographic database
Bibliographic database
A bibliographic database is a database of bibliographic records, an organized digital collection of references to published literature, including journal and newspaper articles, conference proceedings, reports, government and legal publications, patents, books, etc...

, an index of citation
Citation
Broadly, a citation is a reference to a published or unpublished source . More precisely, a citation is an abbreviated alphanumeric expression Broadly, a citation is a reference to a published or unpublished source (not always the original source). More precisely, a citation is an abbreviated...

s between publications, allowing the user to easily establish which later documents cite which earlier documents. The first citation indices were legal citator
Citator
In legal research, a citator is a citation index of legal resources, one of the best-known of which in the United States is Shepard's Citations. Given a reference of a legal decision, a citator allows the researcher to find newer documents which cite the original document and thus to reconstruct...

s such as Shepard's Citations
Shepard's Citations
In legal research, Shepard's Citations is a citator, a list of all the authorities citing a particular case, statute, or other legal authority. The verb Shepardizing refers to the process of consulting Shepard's to see if a case has been overturned, reaffirmed, questioned, or cited by later cases...

 (1873). In 1960, Eugene Garfield
Eugene Garfield
Eugene "Gene" Garfield is an American scientist, one of the founders of bibliometrics and scientometrics. He received a PhD in Structural Linguistics from the University of Pennsylvania in 1961. Dr. Garfield was the founder of the Institute for Scientific Information , which was located in...

's Institute for Scientific Information
Institute for Scientific Information
The Institute for Scientific Information was founded by Eugene Garfield in 1960. It was acquired by Thomson Scientific & Healthcare in 1992, became known as Thomson ISI and now is part of the Healthcare & Science business of the multi-billion dollar Thomson Reuters Corporation.ISI offered...

 (ISI) introduced the first citation index for papers published in academic journal
Academic journal
An academic journal is a peer-reviewed periodical in which scholarship relating to a particular academic discipline is published. Academic journals serve as forums for the introduction and presentation for scrutiny of new research, and the critique of existing research...

s, starting with the Science Citation Index
Science Citation Index
The Science Citation Index is a citation index originally produced by the Institute for Scientific Information and created by Eugene Garfield in 1960, which is now owned by Thomson Reuters. The larger version covers more than 6,500 notable and significant journals, across 150 disciplines, from ...

(SCI), and later expanding to produce the Social Sciences Citation Index
Social Sciences Citation Index
Social Sciences Citation Index is an interdisciplinary citation index product of Thomson Reuters' Healthcare & Science division. It was developed by the Institute for Scientific Information from the Science Citation Index....

(SSCI) and the Arts and Humanities Citation Index
Arts and Humanities Citation Index
The Arts & Humanities Citation Index , also known as Arts & Humanities Search is a citation index, with abstracting and indexing for more than 1,300 arts and humanities journals, and coverage of disciplines that includes social and natural science journals. Part of this database is derived from...

(AHCI). The first automated citation indexing was done by CiteSeer
CiteSeer
CiteSeer was a public search engine and digital library for scientific and academic papers. It is often considered to be the first automated citation indexing system and was considered a predecessor of academic search tools such as Google Scholar and Microsoft Academic Search. It was replaced by...

 in 1997. Other sources for such data include Google Scholar
Google Scholar
Google Scholar is a freely accessible web search engine that indexes the full text of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-reviewed online journals of Europe and America's largest...

.

Major citation indexing services

There are two publishers of general-purpose academic citation indexes, available to libraries by subscription:
  • ISI (now part of Thomson Scientific
    Thomson Scientific & Healthcare
    Thomson Scientific & Healthcare was a division of the Thomson Corporation until 2006.The division then split into two new divisions: Thomson Scientific and Thomson Healthcare.-External links:***...

    ), which publishes the ISI citation indexes in print and compact disc
    Compact Disc
    The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

    . They are now generally accessed through the Web under the name Web of Science
    Web of Science
    ISI Web of Knowledge is an academic citation indexing and search service, which is combined with web linking and provided by Thomson Reuters. Web of Knowledge coverage encompasses the sciences, social sciences, arts and humanities. It provides bibliographic content and the tools to access, analyze,...

    , which is in turn part of the group of databases in the Web of Knowledge.
  • Elsevier
    Elsevier
    Elsevier is a publishing company which publishes medical and scientific literature. It is a part of the Reed Elsevier group. Based in Amsterdam, the company has operations in the United Kingdom, USA and elsewhere....

    , which publishes Scopus
    Scopus
    Scopus, officially named SciVerse Scopus, is a bibliographic database containing abstracts and citations for academic journal articles. It covers nearly 18,000 titles from over 5,000 international publishers, including coverage of 16,500 peer-reviewed journals in the scientific, technical, medical,...

    , available online only, which similarly combines subject searching with citation browsing and tracking in the sciences and social sciences
    Social sciences
    Social science is the field of study concerned with society. "Social science" is commonly used as an umbrella term to refer to a plurality of fields outside of the natural sciences usually exclusive of the administrative or managerial sciences...

    .


Each of these offer an index of citations between publications and a mechanism to establish which documents cite which other documents. They differ widely in cost: the ISI databases and Scopus are subscription databases, the others mentioned are freely available online.

Citation analysis

While citation indexes were originally designed for information retrieval
Information retrieval
Information retrieval is the area of study concerned with searching for documents, for information within documents, and for metadata about documents, as well as that of searching structured storage, relational databases, and the World Wide Web...

 purposes, they are increasingly used for bibliometrics
Bibliometrics
Bibliometrics is a set of methods to quantitatively analyze scientific and technological literature. Citation analysis and content analysis are commonly used bibliometric methods...

 and other studies involving research evaluation. Citation data is also the basis of the popular journal impact factor.

There is a large body of literature on citation analysis
Citation analysis
Citation analysis is the examination of the frequency, patterns, and graphs of citations in articles and books. It uses citations in scholarly works to establish links to other works or other researchers. Citation analysis is one of the most widely used methods of bibliometrics...

, sometimes called scientometrics
Scientometrics
Scientometrics is the science of measuring and analysing science. In practice, scientometrics is often done using bibliometrics which is a measurement of the impact of publications. Modern scientometrics is mostly based on the work of Derek J. de Solla Price and Eugene Garfield...

, a term invented by Vasily Nalimov
Vasily Nalimov
Vasily Nalimov was a Russian philosopher, humanist and wrote on Transpersonal Psychology. His main areas of research were the philosophy of probability and its biological, mathematical, and linguistic manifestations. He also studied the roles of gnosticism and mysticism in science...

, or more specifically bibliometrics
Bibliometrics
Bibliometrics is a set of methods to quantitatively analyze scientific and technological literature. Citation analysis and content analysis are commonly used bibliometric methods...

. The field blossomed with the advent of the Science Citation Index
Science Citation Index
The Science Citation Index is a citation index originally produced by the Institute for Scientific Information and created by Eugene Garfield in 1960, which is now owned by Thomson Reuters. The larger version covers more than 6,500 notable and significant journals, across 150 disciplines, from ...

, which now covers source literature from 1900 on. The leading journals of the field are Scientometrics
Scientometrics
Scientometrics is the science of measuring and analysing science. In practice, scientometrics is often done using bibliometrics which is a measurement of the impact of publications. Modern scientometrics is mostly based on the work of Derek J. de Solla Price and Eugene Garfield...

,
Informetrics, and the Journal of the American Society of Information Science and Technology. ASIST
American Society for Information Science and Technology
The American Society for Information Science and Technology, sometimes abbreviated ASIS&T or ASIST, is a non-profit membership organization for information professionals...

 also hosts an electronic mailing list
Electronic mailing list
An electronic mailing list is a special usage of email that allows for widespread distribution of information to many Internet users. It is similar to a traditional mailing list — a list of names and addresses — as might be kept by an organization for sending publications to...

 called SIGMETRICS at ASIST. This method is undergoing a resurgence based on the wide dissemination of the Web of Science and Scopus subscription databases in many universities, and the universally-available free citation tools such as CiteBase
Citebase
Citebase Search is an experimental, semi-autonomous citation index for the free, online research literature created by Tim Brody at the University of Southampton, UK. It harvests open access e-prints from OAI-PMH compliant archives, parses and links their references and indexes the metadata in a...

, CiteSeerX
CiteSeerX
CiteSeerX is a public search engine and digital library and repository for scientific and academic papers with a focus on computer and information science. It is loosely based on the previous CiteSeer search engine and digital library and is built with a new open source infrastructure, SeerSuite,...

, Google Scholar
Google Scholar
Google Scholar is a freely accessible web search engine that indexes the full text of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-reviewed online journals of Europe and America's largest...

, and the former Windows Live Academic
Windows Live Academic
Live Search Academic was a Web search engine for scholarly literature which existed from 2006–2008; it was part of Microsoft's Live Search group of services. It was similar, rather than equivalent, to Google Scholar in that the users are required to login before accessing the service...

 (now available with extra features as Microsoft Academic Search).

Legal citation
Legal citation
Legal citation is the practice of crediting and referring to authoritative documents and sources. The most common sources of authority cited are court decisions , statutes, regulations, government documents, treaties, and scholarly writing....

 analysis is a citation analysis technique for analyzing legal documents to facilitate the understanding of the inter-related regulatory compliance documents by the exploration the citations that connect provisions to other provisions within the same document or between different documents. Legal citation analysis uses a citation graph extracted from a regulatory document.

History

In a 1965 paper, Derek J. de Solla Price
Derek J. de Solla Price
Derek John de Solla Price was a physicist, historian of science, and information scientist,credited as the father of scientometrics.-Biography:...

 described the inherent linking characteristic of the SCI as "Networks of Scientific Papers". The links between citing and cited papers became dynamic when the SCI began to be published online. The Social Sciences Citation Index
Social Sciences Citation Index
Social Sciences Citation Index is an interdisciplinary citation index product of Thomson Reuters' Healthcare & Science division. It was developed by the Institute for Scientific Information from the Science Citation Index....

 became one of the first databases to be mounted on the Dialog system in 1972. With the advent of the CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....

 edition, linking became even easier and enabled the use of bibliographic coupling
Bibliographic coupling
Bibliographic coupling occurs when two works reference a common third work in their bibliographies. The coupling strength is higher the more citations the two bodies have in common, and this coupling is used to extrapolate how similar the subject matter of the two works is...

 for finding related records. In 1973 Henry Small published his classic work on Co-Citation analysis which became a self-organizing
Self-organization
Self-organization is the process where a structure or pattern appears in a system without a central authority or external element imposing it through planning...

 classification system that led to document clustering
Document clustering
Document clustering is closely related to the concept of data clustering. Document clustering is a more specific technique for unsupervised document organization, automatic topic extraction and fast information retrieval or filtering.A web search engine often returns thousands of pages in...

 experiments and eventually an "Atlas of Science" later called "Research Reviews".

The inherent topological and graphical nature of the worldwide citation network which is an inherent property of the scientific literature
Scientific literature
Scientific literature comprises scientific publications that report original empirical and theoretical work in the natural and social sciences, and within a scientific field is often abbreviated as the literature. Academic publishing is the process of placing the results of one's research into the...

 was described by Ralph Garner (Drexel University
Drexel University
Drexel University is a private research university with the main campus located in Philadelphia, Pennsylvania, USA. It was founded in 1891 by Anthony J. Drexel, a noted financier and philanthropist. Drexel offers 70 full-time undergraduate programs and accelerated degrees...

) in 1965.

The use of citation counts to rank journals was a technique used in the early part of the nineteenth century but the systematic ongoing measurement of these counts for scientific journals was initiated by Eugene Garfield at the Institute for Scientific Information who also pioneered the use of these counts to rank authors and papers. In a landmark paper of 1965 he and Irving Sher showed the correlation between citation frequency and eminence in demonstrating that Nobel Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

 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. The usual summary measure is known as impact factor
Impact factor
The impact factor, often abbreviated IF, is a measure reflecting the average number of citations to articles published in science and social science journals. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed...

, the number of citations to a journal for the previous two years, divided by the number of articles published in those years. It is widely used, both for appropriate and inappropriate purposes—in particular, the use of this measure alone for ranking authors and papers is therefore quite controversial.

In an early study in 1964 of the use of Citation Analysis in writing the history of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

, Garfield and Sher demonstrated the potential for generating historiographs, topological map
Topological map
In cartography and geology, a topological map is one that has been simplified so that only vital information remains and unnecessary detail has been removed. These maps lack scale, and distance and direction are subject to change and variation, but the relationship between points is maintained...

s of the most important steps in the history of scientific topics. This work was later automated by E. Garfield, A. I. Pudovkin of the Institute of Marine Biology, Russian Academy of Sciences
Russian Academy of Sciences
The Russian Academy of Sciences consists of the national academy of Russia and a network of scientific research institutes from across the Russian Federation as well as auxiliary scientific and social units like libraries, publishers and hospitals....

 and V. S. Istomin of Center for Teaching, Learning, and Technology, Washington State University
Washington State University
Washington State University is a public research university based in Pullman, Washington, in the Palouse region of the Pacific Northwest. Founded in 1890, WSU is the state's original and largest land-grant university...

 and led to the creation of the HistCite
Histcite
HistCite is a software package used for bibliometric analysis and information visualization. It was developed by Eugene Garfield, the founder of the Institute for Scientific Information and the inventor of important information retrieval tools such as Current Contents and the Science Citation...

  software around 2002.

Autonomous citation indexing was introduced in 1998 by Lee Giles
Lee Giles
C. Lee Giles is the David Reese Professor at the College of Information Sciences and Technology at the Pennsylvania State University. He is also Professor of Computer Science and Engineering, Professor of Supply Chain and Information Systems, and Director of the Intelligent Systems Research...

, Steve Lawrence
Steve Lawrence
Steve Lawrence is an American singer and actor, perhaps best known as a member of a duo with his wife Eydie Gormé, billed as "Steve and Eydie"...

 and Kurt Bollacker
Kurt Bollacker
Dr. Kurt Bollacker is a computer scientist with a research background in the areas of machine learning, digital libraries, semantic networks, and electro-cardiographic modeling. He received a Ph.D. in Computer Engineering from The University Of Texas At Austin...

  and enabled automatic algorithmic extraction and grouping of citations for any digital academic and scientific document. Where previous citation extraction was a manual process, citation measures could now scale up and be computed for any scholarly and scientific field and document venue, not just those selected by organizations such as ISI. This led to the creation of new systems for public and automated citation indexing, the first being CiteSeer
CiteSeer
CiteSeer was a public search engine and digital library for scientific and academic papers. It is often considered to be the first automated citation indexing system and was considered a predecessor of academic search tools such as Google Scholar and Microsoft Academic Search. It was replaced by...

 (now CiteSeerX
CiteSeerX
CiteSeerX is a public search engine and digital library and repository for scientific and academic papers with a focus on computer and information science. It is loosely based on the previous CiteSeer search engine and digital library and is built with a new open source infrastructure, SeerSuite,...

, soon followed by Cora (recently reborn as Rexa), which focused primarily on the field of computer and information science
Information science
-Introduction:Information science is an interdisciplinary science primarily concerned with the analysis, collection, classification, manipulation, storage, retrieval and dissemination of information...

. These were later followed by large scale academic domain citation systems such as the Google Scholar and previously Microsoft Academic. Such autonomous citation indexing is not yet perfect in citation extraction or citation clustering with an error rate estimated by some at 10% though a careful statistical sampling has yet to be done. This has resulted in such authors as Ann Arbor
Ann Arbor, Michigan
Ann Arbor is a city in the U.S. state of Michigan and the county seat of Washtenaw County. The 2010 census places the population at 113,934, making it the sixth largest city in Michigan. The Ann Arbor Metropolitan Statistical Area had a population of 344,791 as of 2010...

, Milton Keynes
Milton Keynes
Milton Keynes , sometimes abbreviated MK, is a large town in Buckinghamshire, in the south east of England, about north-west of London. It is the administrative centre of the Borough of Milton Keynes...

, and Walton Hall
Walton Hall, Milton Keynes
Walton Hall is a district in Milton Keynes, in the English county of Buckinghamshire, and is the location of the campus and offices of The Open University. The University campus covers 48 hectares and the first buildings were designed by Maxwell Fry & Jane Drew in 1969.It is in the ancient parish...

 being credited with extensive academic output. SCI claims to create automatic citation indexing through purely programmatic methods. Even the older records have a similar magnitude of error.

See also

  • Impact factor
    Impact factor
    The impact factor, often abbreviated IF, is a measure reflecting the average number of citations to articles published in science and social science journals. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed...

  • Citation impact
    Citation impact
    Citation is the process of acknowledging or citing the author, year, title, and locus of publication of a source used in a published work. Such citations can be counted as measures of the usage and impact of the cited work. This is called citation analysis or bibliometrics...

  • Citation index
    Citation index
    A citation index is a kind of bibliographic database, an index of citations between publications, allowing the user to easily establish which later documents cite which earlier documents. The first citation indices were legal citators such as Shepard's Citations...

  • Eigenfactor
    Eigenfactor
    The Eigenfactor score, developed by Jevin West and Carl Bergstrom at the University of Washington, is a rating of the total importance of a scientific journal...

  • Scopus
    Scopus
    Scopus, officially named SciVerse Scopus, is a bibliographic database containing abstracts and citations for academic journal articles. It covers nearly 18,000 titles from over 5,000 international publishers, including coverage of 16,500 peer-reviewed journals in the scientific, technical, medical,...

  • H-index
    H-index
    The h-index is an index that attempts to measure both the productivity and impact of the published work of a scientist or scholar. The index is based on the set of the scientist's most cited papers and the number of citations that they have received in other publications...

     or Hirsch number
  • Citation analysis
    Citation analysis
    Citation analysis is the examination of the frequency, patterns, and graphs of citations in articles and books. It uses citations in scholarly works to establish links to other works or other researchers. Citation analysis is one of the most widely used methods of bibliometrics...

  • Acknowledgment index
    Acknowledgment index
    An acknowledgment index is a method for indexing and analyzing acknowledgements in the scientific literature and, thus, quantifies the impact of acknowledgments. Typically, a scholarly article has a section where the authors acknowledge entities such as funding, technical staff, colleagues, etc....

  • CiteSeer
    CiteSeer
    CiteSeer was a public search engine and digital library for scientific and academic papers. It is often considered to be the first automated citation indexing system and was considered a predecessor of academic search tools such as Google Scholar and Microsoft Academic Search. It was replaced by...

  • CiteSeerX
    CiteSeerX
    CiteSeerX is a public search engine and digital library and repository for scientific and academic papers with a focus on computer and information science. It is loosely based on the previous CiteSeer search engine and digital library and is built with a new open source infrastructure, SeerSuite,...

  • Scientific journal
    Scientific journal
    In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...

  • Science Citation Index
    Science Citation Index
    The Science Citation Index is a citation index originally produced by the Institute for Scientific Information and created by Eugene Garfield in 1960, which is now owned by Thomson Reuters. The larger version covers more than 6,500 notable and significant journals, across 150 disciplines, from ...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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