System and method for topical document searching

Systems and methods are providing for searching for documents within topically-defined clusters. A search space is defined, starting with one or more source documents, by examining references from one documents to another and following the networks of references to some level of indirection. Depending on the embodiment, references may be followed from a document containing a reference to a referred-to document, or from a referred-to document to a document containing a reference, or both. Once a search space has been defined, a query is executed, and documents within the search space that satisfy the query parameters are identified.In certain embodiments of the invention, the documents primarily relate to legal materials, and one or more source documents are associated with one or more topics within a topic directory. In such embodiments, a search query may be limited to one or more selected topics by executing the search query within a search space defined using the associated document or documents as the source.