Gaya APA

Obert, L., Duvall, W, I. (1967). Rock Mechanics and the Design of Structures in Rock . New York: John Wiley & Sons, Inc..

Gaya MLA

Obert, Leonard., Duvall, Wilbur, I. "Rock Mechanics and the Design of Structures in Rock". New York: John Wiley & Sons, Inc., 1967. Text.