Official road map, Montana / Conoco Travel Bureau.
MLA
Company, H. M. Gousha. Official Road Map, Montana / Conoco Travel Bureau. H.M. Gousha, 0AD. https://collections.library.yale.edu/catalog/15818317.
APA, 6th edition
Company, H. M. G. (0 C.E.). Official road map, Montana / Conoco Travel Bureau. [Road maps]. H.M. Gousha, https://collections.library.yale.edu/catalog/15818317.