Dyfyniad APA

Johnson, R. B., & Degraff, V. J. (1988). Principles of Engineering Geology. John Wiley.

Dyfyniad Arddull Chicago

Johnson, Robert. B., and V. Jerome Degraff. Principles of Engineering Geology. New Delhi: John Wiley, 1988.

Dyfyniad MLA

Johnson, Robert. B., and V. Jerome Degraff. Principles of Engineering Geology. John Wiley, 1988.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.