MLA
MacMillan, James M. Writings by James M. Macmillan, on Back of United States Census Document. 1900. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 17. https://digital.library.emory.edu/purl/334fn2z50v-cor.
APA, 6th edition
MacMillan, J. M. (1900). Writings by James M. Macmillan, on back of United States Census document (Box 1, Folder 17) [Notes (documents)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/334fn2z50v-cor.
Chicago
MacMillan, James M. “Writings by James M. Macmillan, on Back of United States Census Document.” Notes (documents). Benjamin T. Watkins Family Papers, 1900. Box 1, Folder 17. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/334fn2z50v-cor.