APA (7e ed.) Bronvermelding

United States. Post Office Dept. (1968). National Zip code directory. [Bureau of Operation.

Chicago (17e ed.) Bronvermelding

United States. Post Office Dept. National Zip Code Directory. Washington: [Bureau of Operation, 1968.

MLA (9e ed.) Bronvermelding

United States. Post Office Dept. National Zip Code Directory. [Bureau of Operation, 1968.

Let op: Deze citaties zijn niet altijd 100% accuraat.