MLA
Sehon, Edmund W., 1808-1876. Letter from Edmund W. Sehon (Louisville, Kentucky) to Robert Paine - February 25, 1851. February 25, 1851. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/532d7wm4hz-cor.
APA, 6th edition
Sehon, Edmund W., 1808-1876. (February 25, 1851)[Letter from Edmund W. Sehon (Louisville, Kentucky) to Robert Paine - February 25, 1851]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/532d7wm4hz-cor.
Chicago
Sehon, Edmund W., 1808-1876, Letter from Edmund W. Sehon (Louisville, Kentucky) to Robert Paine - February 25, 1851, February 25, 1851, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/532d7wm4hz-cor.