1. A computer-implemented method comprising steps of: receiving an original question from a user; generating two or more queries based on the original question; submitting each of the two or more queries to a search engine; for each particular query of the two or more queries, receiving, from the search engine, a separate document set returned as results for that particular query, thereby receiving a plurality of document sets; for each particular document set in the plurality of document sets, identifying concepts to which terms in the particular document set relate, and adding said concepts to a concept set; wherein the steps are performed by one or more computing devices.