The aim of the study is to study empirical use of Bradford's law for decisions concerning information systems in problem based fields, were journals from different disciplines cover relevant information. Results of comparison of the cores in different fields can be used as a base for tailoring an information system. Bradford's law is in the study applied on five databases in the topic "Information retrieval and seeking" in order to compare the size and titles of the core journals. These databases give different views of the same interdisciplinary topic. Problems are relevance judgments, which change the shape of the graphs, and consistency of concepts in the analysis. The results show that Bradford analyses can be useful tools in developing information systems.