APA (7th ed.) Citation

Pettitt, J. M., & Beck, C. B. (1968). Archaeosperma Arnoldii, a cupulate seed from the Upper Devonian of North America.

Chicago Style (17th ed.) Citation

Pettitt, John M., and Charles B. Beck. Archaeosperma Arnoldii, a Cupulate Seed from the Upper Devonian of North America. Ann Arbor, Mich, 1968.

MLA (9th ed.) Citation

Pettitt, John M., and Charles B. Beck. Archaeosperma Arnoldii, a Cupulate Seed from the Upper Devonian of North America. 1968.