Gaya APA

Petersen, M, S., Keith, I, R, J. (1982). Interpreting earth history a manual in historical geology . Iowa: Iowa: WM. C. Brown Company Publishers; 1982.

Gaya MLA

Petersen, Morris, S.., Keith, I., Rigby,, J.. "Interpreting earth history a manual in historical geology". Iowa: Iowa: WM. C. Brown Company Publishers; 1982, 1982. Text.