MLA
Colman, J. M., and E. Stevenson. Letter from E. Stevenson and J. M. Colman (Louisville, Kentucky) to Robert Paine - September 26, 1849. 1849. Pitts Theology Library, Box 1, Folder 20. https://digital.library.emory.edu/purl/525k98sgdg-cor.
APA, 6th edition
Colman, J. M., & Stevenson, E. (1849). Letter from E. Stevenson and J. M. Colman (Louisville, Kentucky) to Robert Paine - September 26, 1849 (Box 1, Folder 20) [Letters (correspondence)]. Pitts Theology Library. https://digital.library.emory.edu/purl/525k98sgdg-cor.
Chicago
Colman, J. M., and E. Stevenson. “Letter from E. Stevenson and J. M. Colman (Louisville, Kentucky) to Robert Paine - September 26, 1849.” Letters (correspondence). Robert Paine Papers, 1828-1882, 1849. Box 1, Folder 20. Pitts Theology Library. https://digital.library.emory.edu/purl/525k98sgdg-cor.