MLA
Hofflinger, Erastus. Letters from Erastus Hofflinger (City Point, near Richmond, Virginia) to His Sister. Hofflinger Was a Member of the 23rd New Jersey Infantry Regiment, Company D - June 20, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 19, Folder 36. https://digital.library.emory.edu/purl/9182jm6534-cor.
APA, 6th edition
Hofflinger, E. (1864). Letters from Erastus Hofflinger (City Point, near Richmond, Virginia) to his sister. Hofflinger was a member of the 23rd New Jersey Infantry Regiment, Company D - June 20, 1864 (Box 19, Folder 36) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/9182jm6534-cor.
Chicago
Hofflinger, Erastus. “Letters from Erastus Hofflinger (City Point, near Richmond, Virginia) to His Sister. Hofflinger Was a Member of the 23rd New Jersey Infantry Regiment, Company D - June 20, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 19, Folder 36. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/9182jm6534-cor.