12. The system according to claim 11 , wherein the selecting a set of the identified documents includes using a defined algorithm to identify a quasi-minimal set of the identified documents.
11. A system for retrieving documents, comprising: a computer device comprising at least one distinct software module, each distinct software module being embodied on a tangible computer-readable medium; a memory; and at least one processor coupled to the memory and operative for: searching through a given index to identify a candidate answer for an input query from a user; after the candidate answer is identified, identifying a logical proof of the candidate answer, including using the candidate answer as a conclusion of the logical proof, and identifying a sequence of premises of the logical proof that logically prove said conclusion, said sequence of premises comprising a plurality of premises; searching through the index for documents establishing said sequence of premises of the logical proof, and identifying a multitude of documents that establish to the sequence of premises of said logical proof; selecting a set of the identified documents that establishes all of the premises of the sequence of premises of the logical proof; and returning the set of the identified documents to the user.