MLA

Henri, Robert, 1865-1929. Correspondence. Box 18, folder 439-440. 1902 Mar. https://collections.library.yale.edu/catalog/10268423.

APA, 6th edition

Henri, Robert, 1865-1929. (["Box 18, folder 439-440"])(1902 Mar)[Correspondence]. https://collections.library.yale.edu/catalog/10268423.