APA

Shrock R. R., Twenhofel w. H., . (2005). Principles of invertebrate paleontology. New Delhi: CBS Publishers.

Chicago

Shrock Robert R, Twenhofel william H, . 2005. Principles of invertebrate paleontology. New Delhi: CBS Publishers.

Harvard

Shrock R. R., Twenhofel w. H., . (2005). Principles of invertebrate paleontology. New Delhi: CBS Publishers.

MLA

Shrock Robert R, Twenhofel william H, . Principles of invertebrate paleontology. New Delhi: CBS Publishers. 2005.