1. A method for retrieving relevant documents in a corpus of documents based on a search query, the method comprising the steps of: storing the corpus of documents in a storage device; inputting the corpus of documents and the search query on an input device; generating an index term signature for each index term in the corpus of documents, the index term signature being based on a hash function of a predetermined number of adjacent terms adjacent to the index term; generating a list containing the index terms in the corpus of documents, the list associating each index term with a document identifier and corresponding index term signatures occurring in the document; generating a query signature for the search query excluding a reference term, the query signature being based on the hash function of the adjacent query terms adjacent to the reference term; comparing the query signature to the index term signatures in the list to identify index term signatures that match the query signature, the reference term of the query signature being equivalent to a searched index term of the list; and outputting a document list indicating the documents that contain the identified index term signatures on an output device.