MLA
Andrew [last name unknown]. Letter from Andrew (Camp Huger, Suffolk, Virginia), to "My dear Mother," regarding family news. Andrew was probably from Beaufort, South Carolina - October 3, [no year provided]. October 3, year unknown. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/119f4qrghd-cor.
APA, 6th edition
Andrew [last name unknown]. (October 3, year unknown)[Letter from Andrew (Camp Huger, Suffolk, Virginia), to "My dear Mother," regarding family news. Andrew was probably from Beaufort, South Carolina - October 3, [no year provided]]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/119f4qrghd-cor.
Chicago
Andrew [last name unknown], Letter from Andrew (Camp Huger, Suffolk, Virginia), to "My dear Mother," regarding family news. Andrew was probably from Beaufort, South Carolina - October 3, [no year provided], October 3, year unknown, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/119f4qrghd-cor.