MLA
Cobb, Lamar. Letter from Lamar Cobb (Macon, Georgia) to Henry L. Beman (Atlanta, Georgia), Regarding Payment of Troops - June 17, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 2, Folder 26. https://digital.library.emory.edu/purl/023vt4b9dx-cor.
APA, 6th edition
Cobb, L. (1864). Letter from Lamar Cobb (Macon, Georgia) to Henry L. Beman (Atlanta, Georgia), regarding payment of troops - June 17, 1864 (Box 2, Folder 26) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b9dx-cor.
Chicago
Cobb, Lamar. “Letter from Lamar Cobb (Macon, Georgia) to Henry L. Beman (Atlanta, Georgia), Regarding Payment of Troops - June 17, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 2, Folder 26. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/023vt4b9dx-cor.