Gaya APA

Zein, U, H, H., Keller, E, A. (1976). Environmental Geology . Columbus, Ohio: Bell and Howell Comp..

Gaya MLA

Zein, Umar;, Habib,, Hadiki., Keller, Edward, A.. "Environmental Geology". Columbus, Ohio: Bell and Howell Comp., 1976. Text.