MLA

Montagu, Charles, Duke of Manchester, 1660?-1722. R. Yard to the E of M, on the subject of Mills, Lord Drummond's priest, etc. (Nearly all in cipher, undeciphered) Whitehall. Box 2, folder 51. 1699 Oct 16. https://collections.library.yale.edu/catalog/16601175.

APA, 6th edition

Montagu, Charles, Duke of Manchester, 1660?-1722. (["Box 2, folder 51"])(1699 Oct 16)[R. Yard to the E of M, on the subject of Mills, Lord Drummond's priest, etc. (Nearly all in cipher, undeciphered) Whitehall]. https://collections.library.yale.edu/catalog/16601175.