MLA

Balguy, John, 1686-1748. [Autograph letter signed] 1746-7 February 3, Sheffield [to] Thomas Balguy, St. Johns College, Cambridge. Folder 6. 1746-7 February 3. https://collections.library.yale.edu/catalog/10000033.

APA, 6th edition

Balguy, John, 1686-1748. (["Folder 6"])(1746-7 February 3)[[Autograph letter signed] 1746-7 February 3, Sheffield [to] Thomas Balguy, St. Johns College, Cambridge]. https://collections.library.yale.edu/catalog/10000033.