FAQ & Notes
- What is Times Cited?
- What is LCS?
- What is the Web of Science?
- What is “HistCite” and how is it used in the study?
- What is the H-Index?
- What are “outer” references?
- Data for the Kidney Transplant 1946-1979 collection.
- Data for the Liver Transplant 1945-1992 collection.
- Data for the Chimerism and Transplantation HistCite collection
- Data for the Papers Citing TE Starzl HistCite Collection.
- What are ‘1st Author’ publications?
- What are “papers”?
What is Times Cited?
Generally speaking “Times Cited” refers to the number of times a publication has been cited by other publications in the scientific, peer-review literature. In citation studies of impact, the Times Cited number is usually the key characteristic defining exceptional publications that have made a significant impact in a certain area of science.
The Thomson Reuters’ citation database of peer-review literature, the ISI Web of Science database was used to collect data for these analyses. Because the ISI Web of Science database includes and indexes each publication’s cited references list, it can provide for each record a “Times Cited” figure based on the entire collection of its indexed publications.
In this citation analysis of Dr. Starzl’s scientific publications, the “Times Cited” figure does not refer to the ISI Web of Science “Times Cited” count, but to the LCS score as calculated by the HistCite software.
What is LCS?
LCS is the “Local Citation Score”. This is the number of times the publication has been cited by other publications in the HistCite collection. Because of the differences in how scientific fields produce their professional literature, each field has its own publication and citation norms. If the HistCite collection is crafted to represent a particular field or subfield, the LCS reveals the relative impact of a publication to the field represented by the collection. This helps to normalize the impact number (Times Cited) of publications specific to the field as defined by the HistCite collection.
What is the Web of Science?
The Thomson Reuters ISI Web of Science is a collection of databases of peer-review literature from a wide range of disciplines including scientific fields. In addition to indexing typical bibliographic information like authors, journal and abstract, the database indexes the cited reference list of each publication. This essential data for conducting citation studies and Web of Science is well known as a standard source of information in the citation based studies.
What is “HistCite” and how is it used in the study?
HistCite is a citation analysis software tool. It was created by Dr. Eugene Garfield and is currently owned by Thomson Reuters and is available free of charge for Web of Knowledge (or WoS?) subscribers. While HistCite contains many useful features, in this study HistCite was used to… manage the data from WoS, allow users to search the collection, and correct incorrect data and standardize citations to non-WoS records. HistCite also calculates each publication’s LCS score and prepares a list of the collection’s cited references ordered by frequency. This list highlights the publications which are most cited by the collection.
What is the H-Index?
The H-Index was proposed by Jorge E. Hirsh.
A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np − h) papers have no more than h citations each.
This provides a score that takes into account publication output as well as times cited.
What are “outer references”?
After processing a collection of data, the HistCite software examines each cited reference of all the records and creates a list of all unique cited references ordered by frequency they are found in the collection. Some of the references may be for publications that are present as a record in the data; these are sometimes called inner references because they point to a publication that is “in” the collection. Many more of the references are for publications that are not present in the collection; these are sometimes called outer references because they are outside the data.
Data for the Kidney Transplantation,
WoS Search conducted 8-16-2012.
Title=((kidney* or renal*) AND (graft* OR allograft* OR homograft* OR transplant* OR homotransplant*))
Refined by: Publication Years=( 1946-1979 )
Databases=SCI-EXPANDED, SSCI, A&HCI Timespan=All Years Lemmatization=Off
AND several papers listed at the top of the cited references list were also added to the collection such that the top 2% (~128 publications) most cited publications were present as source records in the assembled collection.
Data for Liver Transplantation, 1945-1992
6289 records found in a WoS Search for:
Title=(liver OR hepatic*) AND
Title=(transplant* OR allograft* OR homograft* OR graft* OR homotransplant* OR allotransplant* OR autograft* OR isograft*)
Databases=SCI-E, SSCI, A&HCI
6326 records downloaded from WoS 8-28-2012. 6289 unique records captured in HistCite collection. The remaining 37 were removed as duplicates. Edited 8-29-2012 to standardize variant references for Experience in Hepatic Transplantation. Also, added 7 publications (4 from WoS) identified from the outer references list, such that the top 1% (63 items) of all cited publications are included as records in the collection.
If the publication was not located in the Web of Science database, it was added manually.
This process identified articles which were not found in the initial search of the WoS Database but were nether-the-less important to the literature of the field by virtue of their outstanding LCS number.
Data for the Chimerism and Transplantation
The "Chimerism and Transplantation" HistCite collection [provide link to collection?] was created by searching the Web of Science database on 8-10-2012.
8,998 papers were downloaded from Web of Science using the following search terms: [Topic=((chimer* OR microchimer*) AND (graft* OR allograft* OR homograft* OR transplant*)) Timespan=1950-01-01 - 2011-12-31. Databases=SCI-EXPANDED, SSCI, A&HCI. Lemmatization=Off.]
After adding these records to the database, the HistCite’s Cited References List was consulted. Individual publications were added to the collection if they were found in the top of the list of most cited references. This continued until the top 2% of the most cited publications were present as source records in the collection. This process added 86 papers to the collection, including two records that were added from PubMed database. This process identified articles which were not found in the initial search of the WoS Database but were nether-the-less important to the literature of the field by virtue of their outstanding LCS number.
In order to cover this crossover discipline during the years in which TE Starzl was publishing on the topic, I used a topic search instead of a title search as it resulted in a more robust sample.
5670 papers downloaded from Web of Science. Topic=((chimer* OR microchimer*) AND (graft* OR allograft* OR homograft* OR transplant*)) Timespan=1991-01-01 - 2005-12-31. Databases=SCI-EXPANDED, SSCI, A&HCI. Lemmatization=Off <hr> AND<hr> 81 papers added from the cited references list so that the top 2% of the most cited papers are included in the collection.
Data for the Papers Citing TE Starzl HistCite Collection
This collection was assembled by searching the Web of Science database. The search was conducted July, 2012 and includes data up to the year 2011. The collection includes all papers found in a Web of Science Cited Reference search where the cited author is "Starzl TE". The collection was subsequently edited to standardize references to highly cited book publications. The collection also includes publications by TE Starzl. Highly-cited publications by TE Starzl that were not found in the Web of Science database were added manually.
What are “1st Author” publications?
In many areas of science, published documents are generally the product of many individual contributions. For example, in the Kidney Transplant collection, for all records the average number of authors per paper is 3.7. Collaboration is considered an important aspect of successful scientific endeavors; however, multi-author publications are problematic when counting citations. Should each co-author be given equal credit for a cited publication or should the credit be divided proportionally?
The HistCite software credits each author with a full citation credit that an individual paper receives. For example a paper with 5 authors is cited 75 times. When comparing authors in the collection and the sum of their publication’s times cited score, each of the five authors will receive the publication’s full 75 citations.
In order to provide an alternative count to counter-balance the effect of highly-cited multi-authored publications, this citation study of Dr. Starzl’s work also includes for each author, the sum times cited of the author’s 1st author publications. In other words, when calculating the sum times cited figure for each author, only those publication’s times cited counts are summed where the author is listed as the 1st author.
What are “papers”?
(and other document type terms explained)
In the world of scientific publishing, there are different types of writing which are used for different purposes. It is sometimes useful to distinguish between these different types of publications because each type may exhibit unique citation patterns. However the term “papers” is used here generically to refer to any type of scientific publication.
Articles and reviews are two important document types in scientific literature. An article presents “research on original works” (from ISI document type definition help page.) and a review usually does not present new information but instead offers an overview or synthesis of previously published material.