Bibliographic coupling and its application to research-front and other core documents

Based on previous findings and theoretical considerations, it was suggested that bibliographic coupling could be combined with a cluster method to provide a method for science mapping, complementary to the prevailing co-citation cluster analytical method. The complete link cluster method was on theoretical grounds assumed to provide a suitable cluster method for this purpose. The objective of the study was to evaluate the proposed method's capability to identify coherent research themes. Applying a large multidisciplinary test bed comprising more than 600,000 articles and 17 million references, the proposed method was tested in accordance with two lines of mapping. In the first line of mapping, all significant (strong) links connecting ‘core documents’ (strongly and frequently coupled documents) in clusters with any other core document was mapped. This resulted in a depiction of all significant artificially broken links between core documents in a cluster and core documents extrinsic to that cluster. The second line of mapping involved the application of links between clusters only. They were used to successively merge clusters on two subsequent levels of fusion, where the first generation of clusters were considered objects for a second clustering, and the second generation of clusters gave rise to a final cluster fusion. Changes of cluster composition on the three levels were evaluated with regard to several variables. Findings showed that the proposed method could provide with valid depictions of current research, though some severe restrictions would adhere to its application.