MLA
Holt, Joseph, 1807-1894. Letter from Joseph Holt (Washington, D.C.) to L. S. Bell - January 14, 1861. January 14, 1861. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/986b2rbq3j-cor.
APA, 6th edition
Holt, Joseph, 1807-1894. (January 14, 1861)[Letter from Joseph Holt (Washington, D.C.) to L. S. Bell - January 14, 1861]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/986b2rbq3j-cor.
Chicago
Holt, Joseph, 1807-1894, Letter from Joseph Holt (Washington, D.C.) to L. S. Bell - January 14, 1861, January 14, 1861, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/986b2rbq3j-cor.