MLA
Halliday, Dickerson W., 1836-1862. Letter from Dickerson W. Halliday (Richmond, Virginia) to Anna Humber (Lumpkin, Georgia). Dickerson served in the 2nd Georgia Infantry Regiment - October 20, 1861. October 20, 1861. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/68605qfvs2-cor.
APA, 6th edition
Halliday, Dickerson W., 1836-1862. (October 20, 1861)[Letter from Dickerson W. Halliday (Richmond, Virginia) to Anna Humber (Lumpkin, Georgia). Dickerson served in the 2nd Georgia Infantry Regiment - October 20, 1861]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/68605qfvs2-cor.
Chicago
Halliday, Dickerson W., 1836-1862, Letter from Dickerson W. Halliday (Richmond, Virginia) to Anna Humber (Lumpkin, Georgia). Dickerson served in the 2nd Georgia Infantry Regiment - October 20, 1861, October 20, 1861, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/68605qfvs2-cor.