MLA
Houston, Elizabeth Price. Letter from Elizabeth Price Houston to Harry Stone Certifying Authenticity of the Star from the Uniform of Robert E. Lee. 1936. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 10, Folder 5. https://digital.library.emory.edu/purl/914nk98tjd-cor.
APA, 6th edition
Houston, E. P. (1936). Letter from Elizabeth Price Houston to Harry Stone certifying authenticity of the star from the uniform of Robert E. Lee (Box 10, Folder 5) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/914nk98tjd-cor.
Chicago
Houston, Elizabeth Price. “Letter from Elizabeth Price Houston to Harry Stone Certifying Authenticity of the Star from the Uniform of Robert E. Lee.” Letters (correspondence). Civil War Collection, 1936. Box 10, Folder 5. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/914nk98tjd-cor.