APA (7th ed.) Citation

Wanless, H. R., & Siever, R. (1956). Classification of the Pennsylvanian rocks of Illinois as of 1956. [publisher not identified].

Chicago Style (17th ed.) Citation

Wanless, Harold R., and Raymond Siever. Classification of the Pennsylvanian Rocks of Illinois as of 1956. Urbana: [publisher not identified], 1956.

MLA (9th ed.) Citation

Wanless, Harold R., and Raymond Siever. Classification of the Pennsylvanian Rocks of Illinois as of 1956. [publisher not identified], 1956.