MLA

Beckford, William, 1760-1844. Beckford, Louisa (typescript copies and photocopies). Box 3, folder 58-61. 1782-89, n.d.. https://collections.library.yale.edu/catalog/17453926.

APA, 6th edition

Beckford, William, 1760-1844. (["Box 3, folder 58-61"])(1782-89, n.d.)[Beckford, Louisa (typescript copies and photocopies)]. https://collections.library.yale.edu/catalog/17453926.