MLA
Thornton, Marianne. Letter from Marianne Thornton to Sarah (Gwynne) Wesley - January 28, 1805. 1805. Pitts Theology Library, Box 3, Folder 8. https://digital.library.emory.edu/purl/491fj6q5qx-cor.
APA, 6th edition
Thornton, M. (1805). Letter from Marianne Thornton to Sarah (Gwynne) Wesley - January 28, 1805 (Box 3, Folder 8) [Correspondence]. Pitts Theology Library. https://digital.library.emory.edu/purl/491fj6q5qx-cor.
Chicago
Thornton, Marianne. “Letter from Marianne Thornton to Sarah (Gwynne) Wesley - January 28, 1805.” Correspondence. Wesleyana Collection, 1805. Box 3, Folder 8. Pitts Theology Library. https://digital.library.emory.edu/purl/491fj6q5qx-cor.