sentences:  In the 1980s, it was available in the U.S. through the Knowledge Index, a low-priced dial-up version of the Dialog service for individual users, which made it popular.For nearly 50 years, the IET has employed scientists to manually review items to be included in Inspec, hand-indexing the literature using their own expertise of the subject area and make a judgement call about which terms and classification codes should be applied.Thanks to this work, a significant thesaurus has been developed which enables content to be indexed far more accurately and in context, which in turn helps end-users discover relevant literature that may otherwise have remained hidden from typical search queries, making Inspec an essential tool for prior art, patentability searches and patent drafting.