MLA
Sandlin, Lucinda E. Letter from Lucinda E. Sandlin (Mooreville, Mississippi) to Her Husband, Alfred W. Sandlin. Alfred W. Sandlin Served in the 1st Mississippi Infantry Regiment and Was Captured at Port Hudson, Louisiana on July 7, 1863 - June 11, 1862. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 11. https://digital.library.emory.edu/purl/6386hdr8j9-cor.
APA, 6th edition
Sandlin, L. E. (1862). Letter from Lucinda E. Sandlin (Mooreville, Mississippi) to her husband, Alfred W. Sandlin. Alfred W. Sandlin served in the 1st Mississippi Infantry Regiment and was captured at Port Hudson, Louisiana on July 7, 1863 - June 11, 1862 (Box 6, Folder 11) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/6386hdr8j9-cor.
Chicago
Sandlin, Lucinda E. “Letter from Lucinda E. Sandlin (Mooreville, Mississippi) to Her Husband, Alfred W. Sandlin. Alfred W. Sandlin Served in the 1st Mississippi Infantry Regiment and Was Captured at Port Hudson, Louisiana on July 7, 1863 - June 11, 1862.” Letters (correspondence). Civil War Collection, 1862. Box 6, Folder 11. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/6386hdr8j9-cor.