The INIS Reference Series defines the rules, standards, formats, codes and authority lists on which the International Nuclear Information System is based. Over the years most manuals have been revised or merged, and further revisions will be issued in the future. The series consists of 10 current manuals, all of which are available in print, on microfiche and many in electronic form, as described below. The Thesaurus gives the Spanish translation of the controlled vocabulary to be used by INIS members to index the literature they report to INIS. This authority ensures consistent subject indexing. Revision 32 of the Spanish version contains 19 422 accepted terms (descriptors) and 6065 forbidden terms (non-descriptors). The terms are listed alphabetically in Spanish, followed by the English equivalent, and with each alphabetic entry a 'word block' containing all the terms associated with that particular entry is displayed.