MLA
Gonne, Maud, 1866-1953. Letter written by Maud Gonne to William Butler Yeats - [July 7, 1910]. July 7, 1910. 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/815p8czc3r-cor.
APA, 6th edition
Gonne, Maud, 1866-1953. (July 7, 1910)[Letter written by Maud Gonne to William Butler Yeats - [July 7, 1910]]. 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/815p8czc3r-cor.
Chicago
Gonne, Maud, 1866-1953, Letter written by Maud Gonne to William Butler Yeats - [July 7, 1910], July 7, 1910, 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/815p8czc3r-cor.