MLA
Post, Philip Sidney, 1833-1895. Letter from Phillip Sidney Post (Headquarters, 2nd Bridgade, 1st Division, 4th Army Corps, near Atlanta, Georgia) to "Miss Mollie S." - August 18, 1864 (typescript). August 18, 1864. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xj39-cor.
APA, 6th edition
Post, Philip Sidney, 1833-1895. (August 18, 1864)[Letter from Phillip Sidney Post (Headquarters, 2nd Bridgade, 1st Division, 4th Army Corps, near Atlanta, Georgia) to "Miss Mollie S." - August 18, 1864 (typescript)]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xj39-cor.
Chicago
Post, Philip Sidney, 1833-1895, Letter from Phillip Sidney Post (Headquarters, 2nd Bridgade, 1st Division, 4th Army Corps, near Atlanta, Georgia) to "Miss Mollie S." - August 18, 1864 (typescript), August 18, 1864, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xj39-cor.