  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.
