APA (7e ed.) Bronvermelding

Leffler, G. L. (1952). Seasonal changes in Pennsylvania business.

Chicago (17e ed.) Bronvermelding

Leffler, George Leland. Seasonal Changes in Pennsylvania Business. State College, 1952.

MLA (8e ed.) Bronvermelding

Leffler, George Leland. Seasonal Changes in Pennsylvania Business. 1952.