Wilson, R. Michael (2006). Great Train Robberies of the Old West. Guilford, Connecticut: TwoDot (Globe Pequot Press). p. 61–63. ISBN978-0-7627-4150-2.
Parsons, Chuck (2011). Captain John R. Hughes, Lone Star Ranger. Denton, Texas: University of North Texas Press. p. 34. ISBN978-1-57441-304-5.
Alle at the time was at best a county deputy sheriff, and may have lacked jurisdiction as a lawman. de la Garza, Beatriz Eugenia (2003). A Law for the Lion: A Tale of Crime and Injustice in the Borderlands. Austin, Texas: University of Texas Press. p. 34. ISBN978-0-292-70189-2.