MLA
Paine, Robert, 1799-1882. Letter from Robert Paine (Nashville, Tennessee) to William McKendree (Aberdeen, Mississippi) - August 6, 1828. August 6, 1828. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/610wpzgp0b-cor.
APA, 6th edition
Paine, Robert, 1799-1882. (August 6, 1828)[Letter from Robert Paine (Nashville, Tennessee) to William McKendree (Aberdeen, Mississippi) - August 6, 1828]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/610wpzgp0b-cor.
Chicago
Paine, Robert, 1799-1882, Letter from Robert Paine (Nashville, Tennessee) to William McKendree (Aberdeen, Mississippi) - August 6, 1828, August 6, 1828, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/610wpzgp0b-cor.