To ensure that publications are assigned to clusters in a meaningful way, we introduce the notion of stable clusters. Essentially, a cluster is stable if it is insensitive to small changes in the underlying data. Bootstrapping is used to make small changes in the data. It is shown that if we want to have an accurate and detailed clustering, we need to be satisfied with a clustering that doesn’t comprehensively cover all publications. Publications that do not clearly belong to one of the main topics in a field cannot be assigned to a cluster.