MLA
Heth, Henry, 1825-1899. Letter from former Confederate general Henry Heth (Georgetown, South Carolina) to General Marcus I. Wright - April 12, 1881. April 12, 1881. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/358bg79dbm-cor.
APA, 6th edition
Heth, Henry, 1825-1899. (April 12, 1881)[Letter from former Confederate general Henry Heth (Georgetown, South Carolina) to General Marcus I. Wright - April 12, 1881]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/358bg79dbm-cor.
Chicago
Heth, Henry, 1825-1899, Letter from former Confederate general Henry Heth (Georgetown, South Carolina) to General Marcus I. Wright - April 12, 1881, April 12, 1881, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/358bg79dbm-cor.