APA استشهاد

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

استشهاد بنمط شيكاغو

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

MLA استشهاد

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