MLA
Gonne, Maud, 1866-1953. Letter written by Maud Gonne to William Butler Yeats - [February/March 1909]. between 1909-02 and 1909-03. 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/781jh9w336-cor.
APA, 6th edition
Gonne, Maud, 1866-1953. (between 1909-02 and 1909-03)[Letter written by Maud Gonne to William Butler Yeats - [February/March 1909]]. 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/781jh9w336-cor.
Chicago
Gonne, Maud, 1866-1953, Letter written by Maud Gonne to William Butler Yeats - [February/March 1909], between 1909-02 and 1909-03, 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/781jh9w336-cor.