MLA

McClintock, Walter, 1870-1949. Fox, Alex. Box 1, folder 27. 1897 January-1904 May 28, 1930 November 29, undated. https://collections.library.yale.edu/catalog/16701790.

APA, 6th edition

McClintock, Walter, 1870-1949. (["Box 1, folder 27"])(1897 January-1904 May 28, 1930 November 29, undated)[Fox, Alex]. https://collections.library.yale.edu/catalog/16701790.