MLA

Edwards, Jonathan, 1703-1758. 6. 1748 Aug 31. JE. Transcript of a letter to John Erskine, in an unidentified hand .. Box 4, folder 146. 1748 August 31. https://collections.library.yale.edu/catalog/33306369.

APA, 6th edition

Edwards, Jonathan, 1703-1758. (["Box 4, folder 146"])(1748 August 31)[6. 1748 Aug 31. JE. Transcript of a letter to John Erskine, in an unidentified hand .]. https://collections.library.yale.edu/catalog/33306369.