MLA
Kingston, William B. Letter from William B. Kingston to Sarah Wesley, Including Sarah Wesley's Response - August 24, 1817. 1817. Pitts Theology Library, Box 3, Folder 42. https://digital.library.emory.edu/purl/0752fqz6hj-cor.
APA, 6th edition
Kingston, W. B. (1817). Letter from William B. Kingston to Sarah Wesley, including Sarah Wesley's response - August 24, 1817 (Box 3, Folder 42) [Correspondence]. Pitts Theology Library. https://digital.library.emory.edu/purl/0752fqz6hj-cor.
Chicago
Kingston, William B. “Letter from William B. Kingston to Sarah Wesley, Including Sarah Wesley's Response - August 24, 1817.” Correspondence. Wesleyana Collection, 1817. Box 3, Folder 42. Pitts Theology Library. https://digital.library.emory.edu/purl/0752fqz6hj-cor.