MLA
Hiles, Isaac. Letter from Isaac Hiles (Camp near Pilot Knob, [Missouri?]) to "Dear Friends." Hiles Was a Member of the 20th Iowa Infantry Regiment, Company I. Hiles Was in the Battle of Province Grove, Arkansas, December 7, 1862, and in the Siege of Vicksburg. His Letters Describe the Privations and Suffering of War - June 1, 1863 (Photocopy). 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 19, Folder 35. https://digital.library.emory.edu/purl/286nzs7j7h-cor.
APA, 6th edition
Hiles, I. (1863). Letter from Isaac Hiles (Camp near Pilot Knob, [Missouri?]) to "Dear Friends." Hiles was a member of the 20th Iowa Infantry Regiment, Company I. Hiles was in the battle of Province Grove, Arkansas, December 7, 1862, and in the siege of Vicksburg. His Letters describe the privations and suffering of war - June 1, 1863 (photocopy) (Box 19, Folder 35) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/286nzs7j7h-cor.
Chicago
Hiles, Isaac. “Letter from Isaac Hiles (Camp near Pilot Knob, [Missouri?]) to ‘Dear Friends." Hiles Was a Member of the 20th Iowa Infantry Regiment, Company I. Hiles Was in the Battle of Province Grove, Arkansas, December 7, 1862, and in the Siege of Vicksburg. His Letters Describe the Privations and Suffering of War - June 1, 1863 (Photocopy).” Letters (correspondence). Civil War Collection, 1863. Box 19, Folder 35. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/286nzs7j7h-cor.