MLA
Russell, George William, 1867-1935. Letter from George Russell (AE) (Dublin) to Augusta Gregory - October 4, 1897. October 4, 1897. Gregory Family Papers, 1770-1956. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/515bcc2g4w-cor.
APA, 6th edition
Russell, George William, 1867-1935. (October 4, 1897)[Letter from George Russell (AE) (Dublin) to Augusta Gregory - October 4, 1897]. Gregory Family Papers, 1770-1956, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/515bcc2g4w-cor.
Chicago
Russell, George William, 1867-1935, Letter from George Russell (AE) (Dublin) to Augusta Gregory - October 4, 1897, October 4, 1897, Gregory Family Papers, 1770-1956, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/515bcc2g4w-cor.