1. A method for identifying a set of query-relevant keywords comprised in one or more documents obtained from a query, wherein the query need not comprise the keywords, comprising: a) creating a term-weight matrix M comprising one or more document term-weight vectors d, wherein each document term-weight vector d comprises information on the frequency in one of the one or more documents obtained from the terms in the query; b) creating an expanded query term-weight vector q expanded from the query term-weight vector q and the term-weight matrix M ; and c) using the expanded query term-weight vector q expanded and the document term-weight vectors d, locating a set of keywords identified as terms related to the query and also comprised in at least one of the documents, wherein the query need not comprise the keywords.