MLA

Freeman, Walter, 1895-1972. 1915. Unidentified. Box 4, folder 151. 1912-1916. https://collections.library.yale.edu/catalog/10011002.

APA, 6th edition

Freeman, Walter, 1895-1972. (["Box 4, folder 151"])(1912-1916)[1915. Unidentified]. https://collections.library.yale.edu/catalog/10011002.