The UN's Documentation page provides some background on indexes.

The following are a combintation of resources available at the University of Iowa and those freely available on-line.

1. AccessUN . New Canaan, CT: Newsbank, 1950–
   Electronic index to UN masthead documents, official records and selected sales publications including journal articles published since 1950. Permits searching across multiple years on various subjects. Includes full-text resolutions, selected meeting records, and links to UN documents on the Web. Allows searching by document numbers and for speeches by representatives of various countries. Serves also as guide to the corresponding microfiche collection (1994– ).
2. Official Documents System. United Nations. "ODS covers all types of official United Nations documentation, beginning in 1993. Older UN documents are, however, added to the system on a daily basis. ODS also provides access to the resolutions of the General Assembly, Security Council, Economic and Social Council and the Trusteeship Council from 1946 onwards. The system does not contain press releases, UN sales publications, the United Nations Treaty Series or information brochures issued by the Department of Public Information."
   
3. UNBISnet. From the UN's Dag Hammarskjöld Library. Comprehensive official index to UN documents and publications for 1979 forward, and earlier for selected major documents. Includes full text of UN resolutions, voting records, and agendas, plus speech citations for the main UN organs. Includes the library's online catalog with records for non-UN books and journal articles on various topics in international relations.
4. Index to the Proceedings of...
   There are indexes to the "proceedings" of each of four principal organs. These are detailed indexes to the Official Records for each organ (see separate section covering the Official Records), including subject, speaker, and country/corporate name indexes. Most recent years of the GA and ECOSOC indexes also include voting tables:
   • Index to the Proceedings of the Economic and Social Council. (1952– ) HC59 .A1957
   • Index to the Proceedings of the General Assembly. (1950/51– ) JX1977 .A445
   • Index to the Proceedings of the Security Council. (1964– ) JX1977 .A5152
   • Index to the Proceedings of the Trusteeship Council. (1952– ) JX4021 .U3853
5. PAIS International . New York: Public Affairs Information Service, 1915–
   Web and print-based ((Main Reference Z7163 .P9)index to English and foreign language books, pamphlets, journal articles, and government publications in the area of public affairs and public policy.
6. Directory of United Nations Databases and Information Services. New York: Advisory Committee for the Co-ordination of Information Services, 1978–
   JX1977.8 .D6 D57
   Subject guide to the information gathering, storage, and dissemination activities of UN organizations. Includes information about the organization, special databases maintained by the organization, services provided, and the names and addresses of contacts.
7. UNDEX. 1970–1978
   This index served as the general index to UN publishing between the Documents Index and UNDOC. Issued in three series:
   • Series A: Subject Index. (1970–1978) Z6481 .U4
   • Series B: Country Index. (1970–1978) Z6481 .U42
   • Series C: List of Documents Issued. (1974–1979) Z6481 .U43
8. UNDOC: Current Index. 1979–1997
   Z6481 .U44
   The most comprehensive official "printed" index available for publications of the UN published between 1979–1997, including masthead documents, sales publications, and official records.
9. United Nations Documents Index. 1950–
   JX1977 .A2
   First general index to UN masthead documents, sales publications, and official records.
10. International Bibliography. Millwood, NY: Kraus International, 1973–1991.
    Z6481 .I5
    Until it ceased publication in 1991 this was an extremely useful index to publications of the major IGOs, including monographs and journal articles. Includes acquisition information.