MLA
Pierce, George F. (George Foster), 1811-1884. Letter from George F. Pierce (Sacramento, California) to Robert Paine (Aberdeen, Mississippi) - August 24, 1859. August 24, 1859. Robert Paine Papers, 1828-1882. Pitts Theology Library. https://digital.library.emory.edu/purl/8601zcrkmk-cor.
APA, 6th edition
Pierce, George F. (George Foster), 1811-1884. (August 24, 1859)[Letter from George F. Pierce (Sacramento, California) to Robert Paine (Aberdeen, Mississippi) - August 24, 1859]. Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/8601zcrkmk-cor.
Chicago
Pierce, George F. (George Foster), 1811-1884, Letter from George F. Pierce (Sacramento, California) to Robert Paine (Aberdeen, Mississippi) - August 24, 1859, August 24, 1859, Robert Paine Papers, 1828-1882, Pitts Theology Library. https://digital.library.emory.edu/purl/8601zcrkmk-cor.