APA (7th ed.) Zitazioa

Birkeland, P. W. (1999). Soil and geomorphology. U.pr..

Chicago Style (17th ed.) Zitazioa

Birkeland, Peter W. Soil and Geomorphology. Oxford: U.pr., 1999.

MLA (9th ed.) Zitazioa

Birkeland, Peter W. Soil and Geomorphology. U.pr., 1999.