MLA
McKay, William. Receipt to William H. Scott, Sr. from William McKay, December 31, 1887. 1887. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 9. https://digital.library.emory.edu/purl/890rr4xjdm-cor.
APA, 6th edition
McKay, W. (1887). Receipt to William H. Scott, Sr. from William McKay, December 31, 1887 (Box 1, Folder 9) [Receipts (financial records)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xjdm-cor.
Chicago
McKay, William. “Receipt to William H. Scott, Sr. from William McKay, December 31, 1887.” Receipts (financial records). William H. Scott Family Papers, 1848-1982, 1887. Box 1, Folder 9. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/890rr4xjdm-cor.