APA (7th ed.) Citation

Gaddum, L. W., & Knowles, H. L. (1953). Our physical environment: A problem approach. Houghton Mifflin.

Chicago Style (17th ed.) Citation

Gaddum, L. W., and Harold L. Knowles. Our Physical Environment: A Problem Approach. Boston: Houghton Mifflin, 1953.

MLA (9th ed.) Citation

Gaddum, L. W., and Harold L. Knowles. Our Physical Environment: A Problem Approach. Houghton Mifflin, 1953.