MLA

Service, United States. Forest. Natural Forest Regions of South America and Their Characteristic Tree Growth. Issued by the Office of Geography and the Dendrologist, 1911. https://collections.library.yale.edu/catalog/15952267.

APA, 6th edition

Service, U. S. F. (1911). Natural forest regions of South America and their characteristic tree growth. [Maps]. Issued by the Office of Geography and the Dendrologist, https://collections.library.yale.edu/catalog/15952267.