Cita APA (7th ed.)

Wallen, R. N. (1992). Introduction to physical geography. WM C. Brown.

Cita Chicago (17th ed.)

Wallen, Robert N. Introduction to Physical Geography. Boulevard: WM C. Brown, 1992.

Cita MLA (9th ed.)

Wallen, Robert N. Introduction to Physical Geography. WM C. Brown, 1992.