MLA

Edwards, Jonathan, 1703-1758. 6. 1750 Nov 15. JE. Transcript of letter to John Erskine, in an unidentified hand.. Box 5, folder 163. 1750 November 15. https://collections.library.yale.edu/catalog/33306569.

APA, 6th edition

Edwards, Jonathan, 1703-1758. (["Box 5, folder 163"])(1750 November 15)[6. 1750 Nov 15. JE. Transcript of letter to John Erskine, in an unidentified hand.]. https://collections.library.yale.edu/catalog/33306569.