MLA
Early, W. F. Letter from W. F. Early (Camp Marion near Yorktown, Virginia, Cobb's Legion) to John C. Early - June 21, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 14. https://digital.library.emory.edu/purl/4407wm38nf-cor.
APA, 6th edition
Early, W. F. (1862). Letter from W. F. Early (Camp Marion near Yorktown, Virginia, Cobb's Legion) to John C. Early - June 21, 1862 (Box 3, Folder 14) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4407wm38nf-cor.
Chicago
Early, W. F. “Letter from W. F. Early (Camp Marion near Yorktown, Virginia, Cobb's Legion) to John C. Early - June 21, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 3, Folder 14. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/4407wm38nf-cor.