MLA
Doggett, D. S. (David Seth), 1810-1880. Letter from D. S. Doggett (Richmond, Virginia) to Robert Paine - March 22, 1873. March 22, 1873. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/723hx3fghc-cor.
APA, 6th edition
Doggett, D. S. (David Seth), 1810-1880. (March 22, 1873)[Letter from D. S. Doggett (Richmond, Virginia) to Robert Paine - March 22, 1873]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/723hx3fghc-cor.
Chicago
Doggett, D. S. (David Seth), 1810-1880, Letter from D. S. Doggett (Richmond, Virginia) to Robert Paine - March 22, 1873, March 22, 1873, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/723hx3fghc-cor.