MLA
Law, William. Letter from William Law to John Wesley. Pitts Theology Library, Box 4, Folder 36. https://digital.library.emory.edu/purl/665h9w0w9s-cor.
APA, 6th edition
Law, W. Letter from William Law to John Wesley (Box 4, Folder 36) [Correspondence]. Pitts Theology Library. https://digital.library.emory.edu/purl/665h9w0w9s-cor.
Chicago
Law, William. “Letter from William Law to John Wesley.” Correspondence. Wesleyana Collection, n.d. Box 4, Folder 36. Pitts Theology Library. https://digital.library.emory.edu/purl/665h9w0w9s-cor.