MLA
Gonne, Maud, 1866-1953. Letter written by Maud Gonne to William Butler Yeats - [January or February 1893]. 1893. 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/3483j9kg8s-cor.
APA, 6th edition
Gonne, Maud, 1866-1953. (1893)[Letter written by Maud Gonne to William Butler Yeats - [January or February 1893]]. 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/3483j9kg8s-cor.
Chicago
Gonne, Maud, 1866-1953, Letter written by Maud Gonne to William Butler Yeats - [January or February 1893], 1893, 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/3483j9kg8s-cor.