MLA

Kilpatrick, Jack Frederick (1915-1967). Unidentified note. Box 7, folder 566. 1891. https://collections.library.yale.edu/catalog/15492791.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 7, folder 566"])(1891)[Unidentified note]. https://collections.library.yale.edu/catalog/15492791.