APA (7e ed.) Bronvermelding

Keffer, C. A. (1907). Nature studies on the farm: Soils and plants. American Book Co..

Chicago (17e ed.) Bronvermelding

Keffer, Charles A. Nature Studies on the Farm: Soils and Plants. New York: American Book Co., 1907.

MLA (8e ed.) Bronvermelding

Keffer, Charles A. Nature Studies on the Farm: Soils and Plants. American Book Co., 1907.