MLA

Beinecke, Edwin J. (Edwin John), 1886-1970. "52". Box 34, folder 819. undated. https://collections.library.yale.edu/catalog/16609870.

APA, 6th edition

Beinecke, Edwin J. (Edwin John), 1886-1970. (["Box 34, folder 819"])(undated)["52"]. https://collections.library.yale.edu/catalog/16609870.