MLA
[unknown last name], Kate. Letter from Kate [last name unknown] (Norfolk, Virginia) to Fannie Keen (Richmond, Virginia) - April 9, 1863. April 9, 1863. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/187pnvx1n1-cor.
APA, 6th edition
[unknown last name], Kate. (April 9, 1863)[Letter from Kate [last name unknown] (Norfolk, Virginia) to Fannie Keen (Richmond, Virginia) - April 9, 1863]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/187pnvx1n1-cor.
Chicago
[unknown last name], Kate, Letter from Kate [last name unknown] (Norfolk, Virginia) to Fannie Keen (Richmond, Virginia) - April 9, 1863, April 9, 1863, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/187pnvx1n1-cor.