MLA

Douglas, Norman, 1868-1952. Research material. Box 2, folder 23-25. [circa 1915]. https://collections.library.yale.edu/catalog/16454697.

APA, 6th edition

Douglas, Norman, 1868-1952. (["Box 2, folder 23-25"])([circa 1915])[Research material]. https://collections.library.yale.edu/catalog/16454697.