1. A system for thematically grouping documents into clusters, comprising: an extraction module to extract from a plurality of documents, concepts comprising at least one of nouns and noun phrases; a frequency determination module to determine a number of occurrences for each concept within each document; a threshold module to select the documents having the concepts with the occurrences that satisfy a bounded range comprising upper edge conditions and lower edge conditions; a theme generator module to generate themes for the selected documents from the subset of concepts by identifying two or more concepts with common semantic meaning; and a cluster module to generate clusters of the selected documents based on the themes; and a processor to execute the modules.