MLA
Gonne, Maud, 1866-1953. Letter written by Maud Gonne to William Butler Yeats - [ca. 1913]. 1913 approx.. 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/378tb2rdtp-cor.
APA, 6th edition
Gonne, Maud, 1866-1953. (1913 approx.)[Letter written by Maud Gonne to William Butler Yeats - [ca. 1913]]. 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/378tb2rdtp-cor.
Chicago
Gonne, Maud, 1866-1953, Letter written by Maud Gonne to William Butler Yeats - [ca. 1913], 1913 approx., 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/378tb2rdtp-cor.