MLA

Beinecke, Edwin J. (Edwin John), 1886-1970. "73". Box 56, folder 1217. undated. https://collections.library.yale.edu/catalog/16609930.

APA, 6th edition

Beinecke, Edwin J. (Edwin John), 1886-1970. (["Box 56, folder 1217"])(undated)["73"]. https://collections.library.yale.edu/catalog/16609930.