MLA

Henri, Robert, 1865-1929. Correspondence. Box 12, folder 316-317. 1890 Sep. https://collections.library.yale.edu/catalog/17029583.

APA, 6th edition

Henri, Robert, 1865-1929. (["Box 12, folder 316-317"])(1890 Sep)[Correspondence]. https://collections.library.yale.edu/catalog/17029583.