MLA
Mickle, William English Jr., 1872-1942. Letter from William F. Mickle Jr. (Camp near Mobile, Alabama) to James W. Cox. Cox was a colonel in the 2nd Alabama Infantry - June 26, 1898. June 26, 1898. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/559q2bvrb2-cor.
APA, 6th edition
Mickle, William English Jr., 1872-1942. (June 26, 1898)[Letter from William F. Mickle Jr. (Camp near Mobile, Alabama) to James W. Cox. Cox was a colonel in the 2nd Alabama Infantry - June 26, 1898]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/559q2bvrb2-cor.
Chicago
Mickle, William English Jr., 1872-1942, Letter from William F. Mickle Jr. (Camp near Mobile, Alabama) to James W. Cox. Cox was a colonel in the 2nd Alabama Infantry - June 26, 1898, June 26, 1898, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/559q2bvrb2-cor.