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1. Introduction
Citation resources have become an important tool for citation analysis at academic institutions. These resources are used to retrieve citation references for citation analysis in an attempt to measure the impact and contribution of a study to the body of knowledge. ISI Web of Science (WOS) has built a reputation as the oldest citation resource, containing the most prestigious academic journals used for the purpose of citation analysis ([22] Norris and Oppenheim, 2007, p. 141). [5] Dess (2006, p. 8) identifies WOS as the trail blazer for citation resources and for more than 40 years, WOS had no competitors ([19] Meho and Yang, 2006, p. 3).
In 2004 this changed when Elsevier launched Scopus as a multidisciplinary citation resource ([22] Norris and Oppenheim, 2007, p. 163). [5] Dess (2006, p. 8) refers to Scopus as an interdisciplinary citation resource which is marketed for the Science, Technology and Medicine market. According to [17] Manafy (2005, p. 12) the challenge for Scopus was to position itself as a citation resource in a market where WOS held the monopoly.
In addition to Scopus, Google Scholar (GS) also made its appearance in 2004. [8] Harzing and Van der Wal (2008, p. 12) describe Google Scholar as being responsible for the democratisation of citation analysis. Generally, citation resources are used to keep track of who is doing what research in a specific study field and the impact of the research within the discipline. The prolific growth of online citation resources such as Scopus and Google Scholar created new opportunities for academics in terms of citation tracking and citation analysis.
This article presents the first phase results of a longitudinal comparative study of Web of Science (WOS), Scopus, and Google Scholar (GS) for the South African environmental sciences scholarly journals and specifically reports the findings on the export content verification which established whether the citation resources retrieved is a true reflection of the complete content of the journal (e.g. comprehensive set of citation hits). The verification of content therefore reflects not only the completeness of the journal contents, but also the quality (e.g. correctness) of the information represented by the retrieved results.
2. Citations and citation resources
In order to define a citation resource effectively, it is necessary to...