APA (7e ed.) Bronvermelding

Não informado. (1969). Pennsylvania Geology. Bureau of Topographic and Geologic Survey.

Chicago (17e ed.) Bronvermelding

Não informado. Pennsylvania Geology. Harrisburg, Pa: Bureau of Topographic and Geologic Survey, 1969.

MLA (8e ed.) Bronvermelding

Não informado. Pennsylvania Geology. Bureau of Topographic and Geologic Survey, 1969.

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