MLA

Co, Parker Eng. St. Louis-San Francisco Railway and Auxiliary Lines : December 31, 1918 / Parker Engraving Company. Parker Engraving Company, 1918. https://collections.library.yale.edu/catalog/15813045.

APA, 6th edition

Co, P. E. (1918). St. Louis-San Francisco Railway and auxiliary lines : December 31, 1918 / Parker Engraving Company. [Maps]. Parker Engraving Company, https://collections.library.yale.edu/catalog/15813045.