"The Thesaurus contains all searchable keywords except the newest drug names and novel concepts that have arisen since publication. The Thesaurus is laid out in two columns; the left column contains the look-up term and the right column either contains the higher terms of a keyword, the generic name of a proprietary drug name, or refers the seacher to the correct term or alternative terms to use. Higher terms associated with specific keywords are indicated by the abbreviation h.t. and are found in the right column of the Thesaurus. Whenever the specific keyword appears in the database, the corresponding higher terms also appear and can be searched instead of the specific term if a broader search is required. The abbreviation ‘s.a.’ (see also) is used to indicate a related term which may be worth considering in a search. This Thesaurus is designed to facilitate searching of the Derwent Drug File. The aim of the Thesaurus is to guide the searcher in the selection of correct search terms."