- U.S. Passport Application, Issue Date: 17-May-1924; National Archives Microfilm Publication M1490, Roll 2521, Certificate: 417918; General Records of the Department of State, Record Group 59; National Archives, Washington, D.C.
- Braunlich, Phyllis Cole (1988). Haunted by Home: The Life and Letters of Lynn Riggs. Norman, OK: University of Oklahoma Press. p. 126. ISBN 0-8061-3510-7.
"O'Neill, Rose Cecil (1874–1944)". Women in World History: A Biographical Encyclopedia. Encyclopedia.com. Retrieved 2017-08-21.
Quote: "her brother George O'Neill".
- George O'Neil on IMDb
- George O'Neil at the Internet Broadway Database
- George O'Neil papers, 191?-1935, held by the Billy Rose Theatre Division, New York Public Library for the Performing Arts
- George O'Neil at Library of Congress Authorities, with 9 catalog records