MLA
Gonne, Maud, 1866-1953. Letter written by Maud Gonne to William Butler Yeats - [ca. 1907]. 1907 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/788cfxpr2m-cor.
APA, 6th edition
Gonne, Maud, 1866-1953. (1907 approx.)[Letter written by Maud Gonne to William Butler Yeats - [ca. 1907]]. 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/788cfxpr2m-cor.
Chicago
Gonne, Maud, 1866-1953, Letter written by Maud Gonne to William Butler Yeats - [ca. 1907], 1907 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/788cfxpr2m-cor.