1. A computer-implemented method for generating an output of documents having a predetermined relevance, the method being performed by a relevance detection engine at a server and comprising: receiving an initial document comprising text; receiving a list of documents, each document comprising text, for matching; receiving a minimum substring match length M; normalizing the text of the initial document to form string str, and normalizing the text of the documents of the list of documents to form corresponding strings str k of lengths L k , where k=1 to m; sorting suffixes of the string str with an array to record suffix string positions; calculating a similarity SIM(k) between the string str and each string str k ; searching for a maximal matching length V of the string str and a suffix S(str k ,P) during the calculation of the similarity SIM (k), wherein the suffix S(str k , P) is a suffix of str k starting at position P; determining whether condition V>M is met; if V>M is not met, then incrementing the position P by one; if V>M is met, then adding V/L k to the similarity SIM(k) and incrementing the position P by V; and outputting the similarity SIM(k) between the string str and each string str k .