APA (7th ed.) Citation

Koppe, E. F. (1967). Petrography of coal in the Houtzdale quadrangle: Clearfield County, Pennsylvania. [publisher not identified].

Chicago Style (17th ed.) Citation

Koppe, Edwin F. Petrography of Coal in the Houtzdale Quadrangle: Clearfield County, Pennsylvania. Harrisburg: [publisher not identified], 1967.

MLA (9th ed.) Citation

Koppe, Edwin F. Petrography of Coal in the Houtzdale Quadrangle: Clearfield County, Pennsylvania. [publisher not identified], 1967.