Cita APA (7a ed.)

(1981). The 1981 world book year book.: The annual supplement to the world book encyclopedia (ed.). World book- childcraft international, Inc..

Cita Chicago Style (17a ed.)

The 1981 World Book Year Book.: The Annual Supplement to the World Book Encyclopedia. ed. Chicago: World book- childcraft international, Inc., 1981.

Cita MLA (9a ed.)

The 1981 World Book Year Book.: The Annual Supplement to the World Book Encyclopedia. ed. World book- childcraft international, Inc., 1981.