MLA

Audubon, John James, 1785-1851. Audubon, Victor Gifford. Box 15, folder 693-697. 1833-51, n.d.. https://collections.library.yale.edu/catalog/16445247.

APA, 6th edition

Audubon, John James, 1785-1851. (["Box 15, folder 693-697"])(1833-51, n.d.)[Audubon, Victor Gifford]. https://collections.library.yale.edu/catalog/16445247.