- U.S. Geological Survey Geographic Names Information System: Breen, Colorado
- "Post offices". Jim Forte Postal History. Archived from the original on 6 March 2016. Retrieved 24 June 2016.
- Dawson, John Frank (1954). Place names in Colorado: why 700 communities were so named, 150 of Spanish or Indian origin. Denver, CO: The J. Frank Dawson Publishing Co. p. 11.