Which are the most important papers in the history of a field? On
whose shoulders of giants does an author stand? Where to look for the
intellectual roots of a research topic? These questions can be
answered by using the program CitedReferencesExplorer (CRExplorer).
The CRExplorer is a new software development which is based on the
programs provided at Loet
The CRExplorer uses data from Web of Science (Thomson Reuters)
or Scopus (Elsevier) as input. Publication sets have to be downloaded
including the references cited. The program focusses on the analysis
of the cited references, in particular on the referenced publication
years. Over time, "citation classics" of a field become more
pronounced. When the aggregated citations are plotted along the time
axis, one obtains a "spectrogram" with distinct peaks. CRExplorer
visualizes this spectrogram, cleans the cited references (so-called
"disambiguation"), and uses a smoothing algorithm to suppress the
The method Reference Publication Year Spectroscopy (RPYS) was
developed by Werner Marx, who used it for the first time in the field
of meteorology (see
his study on page 11). For demonstration of the potential of the
method, figure 1 shows the citation classics concerning the discovery
of the “greenhouse effect”, a basic component of climate change.
We downloaded from the Web of Science 3,244 publications
containing the term "greenhouse effect” in the title or in the
abstract or as a keyword. These papers contain 81,126 references to
publications published over 379 years. The graph produced by the
CRExplorer shows three distinct peaks during the 19th century and a
few others during the first half of the 20th century.
The first three pronounced peaks go back to the following
Fourier’s 1927 paper, entitled "Mémoire sur les températures
du globe terrestre et des espaces planétaires", can be seen as the
first decisive publication. Fourier found that the earth is warmer
than expected. He attributed this to the phenomenon that the earth’s
atmosphere is transparent for solar radiation but not for the
infrared radiation from the ground. Thus, he discovered the
(natural) greenhouse effect.
Tyndall's (1861) study, entitled "On the absorption and
radiation of heat by gases and vapours, and on the physical
connexion of radiation, absorption, and conduction", proved that the
earth's atmosphere has a greenhouse effect. He concluded that water
vapour is the principal gas controlling air temperature.
Arrhenius (1896, entitled "On the influence of carbonic acid
in the air upon the temperature of the ground") published the first
study with a calculation of how changes in the levels of carbon
dioxide in the atmosphere can alter the surface temperature through
the greenhouse effect.
The subsequently following peaks can be assigned to the works
of Chamberlin (1898), Arrhenius (1908), and Callendar (1938, 1949).
These are citation classics in the climate change literature. They
deal with the possibility that climatic change results from changes
in the concentration of atmospheric carbon dioxide—thereby supporting
the calculationtheory of Arrhenius. Whereas Chamberlin (1898) and
Callendar (1938, 1949) have been written for scientists, Arrhenius
(1908) book was directed at a general audience.
In sum, the discovery of the earth’s greenhouse effect and the role
of carbon dioxide and water vapor as greenhouse gases are no recent
findings but date back to the beginning of the nineteenth century.
for more information.)
Running CRExplorer & System Requirements
CRExplorer requires a system with Java 8 support. There are two
options to run CRExplorer:
Java Web Start: Click the CRExplorer
Start link to launch CRExplorer directly from this web page using
Java Web Start Launcher. If you start CRExplorer for the first time
your computer system will likely refuse to run the program due to
security reasons. If so, you have to put the URL http://www1.hft-leipzig.de in
the list of exceptions in your Java configuration. Please follow the
official Java instructions on
How can I configure the Exception Site List?. This has to be done
Download: You can download
a runnable JAR file. On most systems a double click on the JAR file
will start CRExplorer. If you want to run the JAR file from command
line please refer to the official Java documentation on
Running JAR-Packaged Software. Here you can also set the heap space
size if you are processing large files.
CRExplorer version 1.6.7 was released on July 5, 2016. This version
includes the following new features and improvements (see New features of
CRExplorer for a detailed description):
Scopus: Using “File” – “Import” – “Scopus”,
CRExplorer reads files from Scopus. The file format “CSV” (including
citations, abstracts and references) should be chosen in Scopus for
Export facilities: Using “File” – “Export” –
“Scopus”, CRExplorer exports files in the Scopus format. Using
“File” – “Export” – “Web of Science”, CRExplorer exports files in
the Web of Science format. These files can be imported in other
bibliometric programs (e.g. VOSviewer).
Space bar: Select a specific cited reference in the
cited references table, press the space bar, and all bibliographic
details of the CR are shown.
Internal file format: Using “File” – “Save”, working
files are saved in the internal file format “*.cre”. The files
include all data including matching results and manual matching
corrections. The files can be opened by using “File” – “Open”.
CRExplorer version 1.6.8 was released on August 29, 2016. This
version includes the following new features and improvements: