MLA
Collins, R. Letter from Mrs. R Collins to G. H. Thompson - August 7, 1889 (Photocopy). 1889. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 3, Folder 49. https://digital.library.emory.edu/purl/423612jn87-cor.
APA, 6th edition
Collins, R. (1889). Letter from Mrs. R Collins to G. H. Thompson - August 7, 1889 (photocopy) (Box 3, Folder 49) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/423612jn87-cor.
Chicago
Collins, R. “Letter from Mrs. R Collins to G. H. Thompson - August 7, 1889 (Photocopy).” Letters (correspondence). Civil War Collection, 1889. Box 3, Folder 49. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/423612jn87-cor.