Gaya APA

Shrock, R, R., Twenhofel, W, H. (1953). Principles of invertabrate paleontology (2nd Ed). New York: McGraw-Hill Book.

Gaya MLA

Shrock, Robert, R.., Twenhofel, William, H.. "Principles of invertabrate paleontology". 2nd Ed New York: McGraw-Hill Book, 1953. Text.