MLA
Pierce, George F. (George Foster), 1811-1884. Letter from George F. Pierce (Culverton, Georgia) to Robert Paine (Aberdeen, Mississippi) - November 9, [no year]. November 9, year unknown. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/426m0cfzwd-cor.
APA, 6th edition
Pierce, George F. (George Foster), 1811-1884. (November 9, year unknown)[Letter from George F. Pierce (Culverton, Georgia) to Robert Paine (Aberdeen, Mississippi) - November 9, [no year]]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/426m0cfzwd-cor.
Chicago
Pierce, George F. (George Foster), 1811-1884, Letter from George F. Pierce (Culverton, Georgia) to Robert Paine (Aberdeen, Mississippi) - November 9, [no year], November 9, year unknown, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/426m0cfzwd-cor.