Scientific literature uses in Geography: indexing and “overlap” in four bibliographic tools

This research aims to evaluate the interest for geographers to use Google Scholar(GS) over the commercial databases Web of Science (WoS), Scopus (multidisciplinary databases), and GeoRef (specialized in geosciences).
To achieve our main objective, we performed searches in order to verify to which extent researchers' citations are covered by the search engine and the three commercial bibliographic databases mentioned. Our sample consists of the citations of three dissertations in Geography presented in the Uliège (Belgium) Department of Geography during the 2014-2015 academic year, respectively in Climatology, Tourism and Geomatics.
In order to have an overview of the results’ “overlap” for the bibliographic tools, and their "unique" contribution, Venn diagrams were constructed for each thesis.
The Venn diagrams indicate that GS finds almost all bibliographic references and returns the greatest number of "unique" results. The “overlap” rates between the commercial databases is very high and GeoRef stands out with very low results.
GS is an important and rich complementary tool, with a more varied panel of publishers, languages and countries of publication.