Παραπομπή APA

Shrock, R. R., & Twenhofel, W. H. (1953). Principles of invertebrate paleontology.2nd ed (2nd ed.). McGraw hill.

Παραπομπή Chicago Style

Shrock, Robert R., και William H. Twenhofel. Principles of Invertebrate Paleontology.2nd Ed. 2nd ed. London: McGraw hill, 1953.

Παραπομπή MLA

Shrock, Robert R., και William H. Twenhofel. Principles of Invertebrate Paleontology.2nd Ed. 2nd ed. McGraw hill, 1953.