MLA

Erdoes, Richard, 1912-2008. "Merida, Mostly People, Cemeteries". Box 43. 1980, undated. https://collections.library.yale.edu/catalog/10251518.

APA, 6th edition

Erdoes, Richard, 1912-2008. (["Box 43"])(1980, undated)["Merida, Mostly People, Cemeteries"]. https://collections.library.yale.edu/catalog/10251518.