Engeln, O. D. v. (1942). Geomorphology, systematic and regional. The Macmillan Company.
Lua i Stíl Chicago (17ú heag.)Engeln, O. D. von. Geomorphology, Systematic and Regional. New York: The Macmillan Company, 1942.
Lua MLA (9ú heag.)Engeln, O. D. von. Geomorphology, Systematic and Regional. The Macmillan Company, 1942.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.