8. An information-retrieval system comprising: a plurality of databases; and a server for providing users access to one or more of the databases, the server including: means for defining and processing a query to generate results comprising documents that include content duplicative of content within one or more other documents within the results; duplicate-determination means for determining whether one or more documents within the results of the query include content duplicative of content within one or more other documents within the results, wherein the duplicate-determination means includes: means for comparing a first document signature for a first one of the documents within the results to a second document signature for a second one of the documents within the results, with each signature based on a plurality of terms and with corresponding positions within the corresponding document; means for comparing, respectively, first and second lengths and first and second temporal features of the first and second documents; means for comparing first and second hash values for the respective first and second documents, with each hash value based on features and positions of the features within its respective document; and wherein the duplicate-determination means is adapted to determine whether the first and second documents are duplicates in response to the results of the means for comparing hash values; means for controlling display of results of the query with at least one of the displayed results indicated as including content duplicative of content in one or more other documents within the results; and means for controlling output of results of the query to a printer or email transmission device, based on user selected options related to output of documents that include content duplicative of content of one or more other documents within the results.
14. The system of claim 8 , wherein means for comparing first and second hash values is executed only if the length or temporal comparison is affirmative.