Day, A. J., & Hoffman, V. (1992). The annual register: A record of world events 1991. Longman Group.
Lua i Stíl Chicago (17ú heag.)Day, Alan J., agus Verena Hoffman. The Annual Register: A Record of World Events 1991. Essex, England: Longman Group, 1992.
Lua MLA (9ú heag.)Day, Alan J., agus Verena Hoffman. The Annual Register: A Record of World Events 1991. Longman Group, 1992.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.