Cita APA (7a ed.)

(1971). The 1971 World Book Year Book. Field Enterprises Educational Corporation.

Cita Chicago Style (17a ed.)

The 1971 World Book Year Book. Chicago, Estados Unidos: Field Enterprises Educational Corporation, 1971.

Cita MLA (9a ed.)

The 1971 World Book Year Book. Field Enterprises Educational Corporation, 1971.