in the Development of the West, C. Scribner's sons, 353 pages. Second opinion doctor. (n.d.). Retrieved September 14, 2020, from http://www.second-opinion-doc.com/horse-bridles-benefits-of-using-a-hackamore.html Williamson, Charles O. (1973) Breaking and Training the Stock Horse. Caxton Printers, Ltd., 6th edition (1st Ed., 1950). Headgear (horse) de:Gebisslose Zäumung#Kalifornische Hackamore (Bosal)