MLA
Mahan, D. H. (Dennis Hart), 1802-1871. An elementary treatise on advanced-guard, out-post, and detachment service of troops, and the manner of posting and handling them in presence of an enemy : intended as a supplement to the system of tactics, adopted for the military service of the United States and especially for the use of officers of militia and volunteers. 1861. Civil War Imprints. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7612ngf5hf-cor.
APA, 6th edition
Mahan, D. H. (Dennis Hart), 1802-1871. (1861)[An elementary treatise on advanced-guard, out-post, and detachment service of troops, and the manner of posting and handling them in presence of an enemy : intended as a supplement to the system of tactics, adopted for the military service of the United States and especially for the use of officers of militia and volunteers]. Civil War Imprints, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7612ngf5hf-cor.
Chicago
Mahan, D. H. (Dennis Hart), 1802-1871, An elementary treatise on advanced-guard, out-post, and detachment service of troops, and the manner of posting and handling them in presence of an enemy : intended as a supplement to the system of tactics, adopted for the military service of the United States and especially for the use of officers of militia and volunteers, 1861, Civil War Imprints, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/7612ngf5hf-cor.