MLA

Walker, Geo. H., and Co. Map of Maine : Rangeley and Megantic District / Published by Walker Lithograph & Publishing Co. Walker Lithograph & Publishing Co. , 0AD. https://collections.library.yale.edu/catalog/15827749.

APA, 6th edition

Walker, G. H., & C. (0 C.E.). Map of Maine : Rangeley and Megantic district / published by Walker Lithograph & Publishing Co. [Maps]. Walker Lithograph & Publishing Co. , https://collections.library.yale.edu/catalog/15827749.