SACO, subject gateways, PCC, Program for Cooperative Cataloging, Library of Congress Subject Headings, LCSH, subject headings, authority files, TERENA, Trans-European Research and Education Networking Association, ROADS, Resource Organisation and Discovery in Subject-based services, MARC21, Virtual International Authority File, VIAF, MACS, Multilingual Access to Subjects, authorities Intestazioni di soggetto, archivi d’autorità