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.
14. The method according to claim 11 , wherein: each of the multitude of documents include references to a given number of the premises of the sequence of premises; and the selecting a set of the identified documents includes selecting the identified documents for the set in order of the number of the premises of the sequence of premises referenced in each of the identified documents.