MLA

McNally, Rand, and Company. Rand McNally Standard Map of Montana with Air Trails ; Rand McNally Standard Map of Montana. Rand McNally, 0AD. https://collections.library.yale.edu/catalog/15814920.

APA, 6th edition

McNally, R., & C. (0 C.E.). Rand McNally standard map of Montana with air trails ; Rand McNally standard map of Montana. [Maps]. Rand McNally, https://collections.library.yale.edu/catalog/15814920.