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 apply a bounded range comprising upper edge conditions and lower edge conditions to the concepts and to select a subset of concepts by removing the concepts that fall outside the bounded range; a theme generator to generate themes from the subset of concepts by identifying two or more concepts with common semantic meaning; and a cluster module to generate clusters of the documents based on the themes.