1. The complete book of bits and bitting;Edwards,2000
2. Duberstein KJ, Johnson EL. Bits 101, B1379, University of Georgia Extensions, http://extension.uga.edu/publications/detail.cfm?number=B1379. Accessed October 7, 2015.
3. Swales F. Improvements in or relating to bits (1906) patent number GB190618657.
4. The effects of various head-gears on horses;Preuschoft;Dtsch Tierärztl Wschr,1999
5. Strain gauge measurement of rein tension during riding: a pilot study;Clayton;Equine Comp Exerc Physiol,2005