(1968). The 1968 World Book Year Book. Field Enterprises Educational Corporation.
Cita Chicago (17th ed.)The 1968 World Book Year Book. Chicago, Estados Unidos: Field Enterprises Educational Corporation, 1968.
Cita MLA (9th ed.)The 1968 World Book Year Book. Field Enterprises Educational Corporation, 1968.
Atenció: Aquestes cites poden no estar 100% correctes.