MLA

Farquhar, Percival, 1864-1953. 1919-1930 April. Box 3, folder 29-41. 1919-1930 April. https://collections.library.yale.edu/catalog/10021363.

APA, 6th edition

Farquhar, Percival, 1864-1953. (["Box 3, folder 29-41"])(1919-1930 April)[1919-1930 April]. https://collections.library.yale.edu/catalog/10021363.