APA-referens (7:e uppl.)

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

Chicago-referens (17:e uppl.)

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

MLA-referens (9:e uppl.)

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