MLA

Hazlitt, William, 1778-1830. AL to his father, William Hazlitt. Box 1, folder 2. 1790 [Jul 24?]. https://collections.library.yale.edu/catalog/9998508.

APA, 6th edition

Hazlitt, William, 1778-1830. (["Box 1, folder 2"])(1790 [Jul 24?])[AL to his father, William Hazlitt]. https://collections.library.yale.edu/catalog/9998508.