MLA
Branson, Maggie A. Letter from Maggie A. Branson (Cassville, Georgia) to "Dear Mildred." She Speaks of the House Being Full of Refugees and That Her Father, 51 Years Old and Her Youngest Brother, 14, Have Been Taken into the Army - No Year [Probably Late 1863 or 1864]. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 35. https://digital.library.emory.edu/purl/5977sqvbst-cor.
APA, 6th edition
Branson, M. A. (1863). Letter from Maggie A. Branson (Cassville, Georgia) to "Dear Mildred." She speaks of the house being full of refugees and that her father, 51 years old and her youngest brother, 14, have been taken into the army - no year [probably late 1863 or 1864] (Box 1, Folder 35) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/5977sqvbst-cor.
Chicago
Branson, Maggie A. “Letter from Maggie A. Branson (Cassville, Georgia) to ‘Dear Mildred." She Speaks of the House Being Full of Refugees and That Her Father, 51 Years Old and Her Youngest Brother, 14, Have Been Taken into the Army - No Year [Probably Late 1863 or 1864].” Letters (correspondence). Civil War Collection, 1863. Box 1, Folder 35. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/5977sqvbst-cor.