MLA
Whelan, Peter, 1802-1871. Letter from Catholic priest, Peter Whelen (Augusta, Georgia) to Mr. and Mrs. Captain Black - August 11, 1866. August 11, 1866. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/102c866v3v-cor.
APA, 6th edition
Whelan, Peter, 1802-1871. (August 11, 1866)[Letter from Catholic priest, Peter Whelen (Augusta, Georgia) to Mr. and Mrs. Captain Black - August 11, 1866]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/102c866v3v-cor.
Chicago
Whelan, Peter, 1802-1871, Letter from Catholic priest, Peter Whelen (Augusta, Georgia) to Mr. and Mrs. Captain Black - August 11, 1866, August 11, 1866, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/102c866v3v-cor.