MLA

Kilpatrick, Jack Frederick (1915-1967). Watt, Johnson (Tsanisini Wadi). Letter, illustrated with a small pencil drawing of two human figures. Box 2, folder 116. undated. https://collections.library.yale.edu/catalog/15492267.

APA, 6th edition

Kilpatrick, Jack Frederick (1915-1967). (["Box 2, folder 116"])(undated)[Watt, Johnson (Tsanisini Wadi). Letter, illustrated with a small pencil drawing of two human figures]. https://collections.library.yale.edu/catalog/15492267.