MLA

Low, David, 1891-1963. Rayner, Fred. Box 8, folder 396. 1943-47, n.d.. https://collections.library.yale.edu/catalog/17280047.

APA, 6th edition

Low, David, 1891-1963. (["Box 8, folder 396"])(1943-47, n.d.)[Rayner, Fred]. https://collections.library.yale.edu/catalog/17280047.