Cita APA (7a ed.)

Hall, C. E., Genth, F. A., & Genth, F. A. The geology of Philadelphia county and of the southern parts of montgomery and bucks.

Cita Chicago Style (17a ed.)

Hall, Charles E., F. A. Genth, y F. A. Genth. The Geology of Philadelphia County and of the Southern Parts of Montgomery and Bucks. Harrisburg.

Cita MLA (8a ed.)

Hall, Charles E., et al. The Geology of Philadelphia County and of the Southern Parts of Montgomery and Bucks.