MLA
Letter from ___(?) Landall to Sister Nancy. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5, Folder 14. https://digital.library.emory.edu/purl/252j6q584n-cor.
APA, 6th edition
Letter from ___(?) Landall to sister Nancy (Box 5, Folder 14). (1863). [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/252j6q584n-cor.
Chicago
“Letter from ___(?) Landall to Sister Nancy.” Letters (correspondence). Civil War Collection, 1863. Box 5, Folder 14. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/252j6q584n-cor.