MLA

Company, H. M. Gousha. Official Road Map of South Dakota / [Prepared for] Conoco Travel Bureau. H.M. Gousha, 0AD. https://collections.library.yale.edu/catalog/15814765.

APA, 6th edition

Company, H. M. G. (0 C.E.). Official road map of South Dakota / [prepared for] Conoco Travel Bureau. [Road maps]. H.M. Gousha, https://collections.library.yale.edu/catalog/15814765.