MLA
Halliday, Dickerson W., 1836-1862. Letter from Dickerson W. Halliday (Camp near Manassas, Virginia) to Anna Humber (Lumpkin, Georgia). Dickerson served in the 2nd Georgia Infantry Regiment - August 29, 1861. August 29, 1861. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3311ns1skg-cor.
APA, 6th edition
Halliday, Dickerson W., 1836-1862. (August 29, 1861)[Letter from Dickerson W. Halliday (Camp near Manassas, Virginia) to Anna Humber (Lumpkin, Georgia). Dickerson served in the 2nd Georgia Infantry Regiment - August 29, 1861]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3311ns1skg-cor.
Chicago
Halliday, Dickerson W., 1836-1862, Letter from Dickerson W. Halliday (Camp near Manassas, Virginia) to Anna Humber (Lumpkin, Georgia). Dickerson served in the 2nd Georgia Infantry Regiment - August 29, 1861, August 29, 1861, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/3311ns1skg-cor.