MLA
Armstrong, Edward J. Power of Attorney Signed by Edward J. Armstrong Jr. (Rockingham County, Virginia), Appointing C.W. Newton as His Attorney to Act for Him in All Matters. 1862. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 9. https://digital.library.emory.edu/purl/5805x69q8z-cor.
APA, 6th edition
Armstrong, E. J. (1862). Power of Attorney signed by Edward J. Armstrong Jr. (Rockingham County, Virginia), appointing C.W. Newton as his attorney to act for him in all matters (Box 1, Folder 9) [Legal documents]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/5805x69q8z-cor.
Chicago
Armstrong, Edward J. “Power of Attorney Signed by Edward J. Armstrong Jr. (Rockingham County, Virginia), Appointing C.W. Newton as His Attorney to Act for Him in All Matters.” Legal documents. Civil War Collection, 1862. Box 1, Folder 9. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/5805x69q8z-cor.