MLA
Russell, George William, 1867-1935. Letter from George Russell (AE) (Dublin) to Augusta Gregory. 1880 to 1920. Gregory Family Papers, 1770-1956. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/395w6m90k7-cor.
APA, 6th edition
Russell, George William, 1867-1935. (1880 to 1920)[Letter from George Russell (AE) (Dublin) to Augusta Gregory]. Gregory Family Papers, 1770-1956, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/395w6m90k7-cor.
Chicago
Russell, George William, 1867-1935, Letter from George Russell (AE) (Dublin) to Augusta Gregory, 1880 to 1920, Gregory Family Papers, 1770-1956, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/395w6m90k7-cor.