MLA
Green, Charles W. Note from Charles W. Green, a Prisoner-of-War at Fort Warren (Boston, Massachusetts) to I. K. Tefft, with Autographs of James M. Mason and John Slidell - January 12, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 40. https://digital.library.emory.edu/purl/28380gb6kz-cor.
APA, 6th edition
Green, C. W. (1862). Note from Charles W. Green, a prisoner-of-war at Fort Warren (Boston, Massachusetts) to I. K. Tefft, with autographs of James M. Mason and John Slidell - January 12, 1862 (Box 3, Folder 40) [Notes]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/28380gb6kz-cor.
Chicago
Green, Charles W. “Note from Charles W. Green, a Prisoner-of-War at Fort Warren (Boston, Massachusetts) to I. K. Tefft, with Autographs of James M. Mason and John Slidell - January 12, 1862.” Notes. Civil War Collection, 1862. Box 3, Folder 40. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/28380gb6kz-cor.