MLA

Audubon, John James, 1785-1851. To Jean Ferdinand Rozier. Box 1, folder 6. 1823 Oct 14. https://collections.library.yale.edu/catalog/16624865.

APA, 6th edition

Audubon, John James, 1785-1851. (["Box 1, folder 6"])(1823 Oct 14)[To Jean Ferdinand Rozier]. https://collections.library.yale.edu/catalog/16624865.