MLA
Mickle, William English Jr., 1872-1942. Letter from William F. Mickle Jr. (Mobile, Alabama) to the United States Secretary of War, Russell A. Alger (Washington, D. C.) - June 23, 1899. June 23, 1899. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/955m905rjm-cor.
APA, 6th edition
Mickle, William English Jr., 1872-1942. (June 23, 1899)[Letter from William F. Mickle Jr. (Mobile, Alabama) to the United States Secretary of War, Russell A. Alger (Washington, D. C.) - June 23, 1899]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/955m905rjm-cor.
Chicago
Mickle, William English Jr., 1872-1942, Letter from William F. Mickle Jr. (Mobile, Alabama) to the United States Secretary of War, Russell A. Alger (Washington, D. C.) - June 23, 1899, June 23, 1899, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/955m905rjm-cor.