MLA
Gonne, Maud, 1866-1953. Letter written by Maud Gonne to William Butler Yeats - June 14 [1918]. June 14, 1918. Maud Gonne and W.B. Yeats Papers, circa 1890-1938. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/27312jm8f3-cor.
APA, 6th edition
Gonne, Maud, 1866-1953. (June 14, 1918)[Letter written by Maud Gonne to William Butler Yeats - June 14 [1918]]. Maud Gonne and W.B. Yeats Papers, circa 1890-1938, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/27312jm8f3-cor.
Chicago
Gonne, Maud, 1866-1953, Letter written by Maud Gonne to William Butler Yeats - June 14 [1918], June 14, 1918, Maud Gonne and W.B. Yeats Papers, circa 1890-1938, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/27312jm8f3-cor.