"A list of keywords or subject headings such as this is known technically as a thesaurus. This is an introduction to the thesaurus for the SoyaScan database, created one record at a time by Soyinfo Center starting in 1985. Keywords, also widely called subject headings, are a 'controlled vocabulary'. You must chose from a given list – as in a dropdown menu. (...) In the body of the Thesaurus, the subject headings and cross references are listed alphabetically."