The following publication contains information about Thomas F. O'Neill:

Article: "Thomas F. O'Neill's Story of the Battle: A 7th Cavalry survivor's account of the Battle of the Little Bighorn" by Bruce Brown • Astonisher.com • Undated • Accessed August 15, 2025.

Article: "Thomas F. O'Neill, First Sergeant, United States Army" • Arlington National Cemetery Website: https://www.arlingtoncemetery.net/toneill.htm • 1994 • Accessed January 3, 2026.