MLA

Howard of Escrick, Edward Howard, Baron, -1675. Fiennes, Armyne, Stapelton, and Hampden to Speaker Leuthall; Edinburgh. Box 1, folder 12. 1641 Sep 3. https://collections.library.yale.edu/catalog/31902526.

APA, 6th edition

Howard of Escrick, Edward Howard, Baron, -1675. (["Box 1, folder 12"])(1641 Sep 3)[Fiennes, Armyne, Stapelton, and Hampden to Speaker Leuthall; Edinburgh]. https://collections.library.yale.edu/catalog/31902526.