MLA

Seymour, George Dudley, 1859-1945. Andre, John. Box 54, folder 719-726. 1834-1936, undated. https://collections.library.yale.edu/catalog/10019503.

APA, 6th edition

Seymour, George Dudley, 1859-1945. (["Box 54, folder 719-726"])(1834-1936, undated)[Andre, John]. https://collections.library.yale.edu/catalog/10019503.