MLA

Montgomery, James, 1771-1854. Southey, Robert. Box 2, folder 91. 1812 Sep 18. https://collections.library.yale.edu/catalog/17301133.

APA, 6th edition

Montgomery, James, 1771-1854. (["Box 2, folder 91"])(1812 Sep 18)[Southey, Robert]. https://collections.library.yale.edu/catalog/17301133.