MLA

Erdoes, Richard, 1912-2008. "Picnic Medium". Box 63. 1975. https://collections.library.yale.edu/catalog/2090019.

APA, 6th edition

Erdoes, Richard, 1912-2008. (["Box 63"])(1975)["Picnic Medium"]. https://collections.library.yale.edu/catalog/2090019.