MLA
Patton, Oliver A. Letter from Oliver A. Patton (Louisville, Kentucky) to "My Dear Gentleman," Regarding the Conditions in the South after the War and Lambasting R. B. Carpenter as a Carpetbagger. Patton Was a Lieutenant Colonel Who Commanded Patton's Battalion Partisan Rangers Which Was Organized in Morgan County, Kentucky, during the Spring of 1863 - December 22, 1868. 1868. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 9, Folder 22. https://digital.library.emory.edu/purl/624jm63zvr-cor.
APA, 6th edition
Patton, O. A. (1868). Letter from Oliver A. Patton (Louisville, Kentucky) to "My Dear Gentleman," regarding the conditions in the South after the war and lambasting R. B. Carpenter as a carpetbagger. Patton was a Lieutenant Colonel who commanded Patton's Battalion Partisan Rangers which was organized in Morgan County, Kentucky, during the spring of 1863 - December 22, 1868 (Box 9, Folder 22) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/624jm63zvr-cor.
Chicago
Patton, Oliver A. “Letter from Oliver A. Patton (Louisville, Kentucky) to ‘My Dear Gentleman," Regarding the Conditions in the South after the War and Lambasting R. B. Carpenter as a Carpetbagger. Patton Was a Lieutenant Colonel Who Commanded Patton's Battalion Partisan Rangers Which Was Organized in Morgan County, Kentucky, during the Spring of 1863 - December 22, 1868.” Letters (correspondence). Civil War Collection, 1868. Box 9, Folder 22. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/624jm63zvr-cor.