Cite

Oil and gas fields of Pennsylvania / compiled under the direction of G.B. Richardson.

MLA

Richardson, G. B. Oil and Gas Fields of Pennsylvania / Compiled under the Direction of G.B. Richardson. U.S. Geological Survey, 1921. https://collections.library.yale.edu/catalog/15952202.

APA, 6th edition

Richardson, G. B. (1921). Oil and gas fields of Pennsylvania / compiled under the direction of G.B. Richardson. [Maps]. U.S. Geological Survey, https://collections.library.yale.edu/catalog/15952202.