The two Journal Citation Reports of the Science Citation Index 2004 and the Social Science Citation Index 2004 were combined in order to analyze and map journals
and specialties at the edges and in the overlap between the two databases. For journals which belong to the overlap (e.g.,
Scientometrics), the merger mainly enriches our insight into the structure which can be obtained from the two databases separately; but
in the case of scientific journals which are more marginal in either database, the combination can provide a new perspective
on the position and function of these journals (e.g., Environment and Planning B — Planning and Design). The combined database additionally enables us to map citation environments in terms of the various specialties comprehensively.
Using the vector-space model, visualizations are provided for specialties that are parts of the overlap (information science,
science & technology studies). On the basis of the resulting visualizations, “betweenness” — a measure from social network
analysis — is suggested as an indicator for measuring the interdisciplinarity of journals.