1. Coil springs as an application of force;Arnold;Int J Orthod,1934
2. Twin wire alignment appliance;Johnson;Int J Orthod,1934
3. The construction and the manipulation of the twin wire mechanism;Johnson;Am J Orthod Oral Surg,1941
4. A study of applied forces as related to the use of elastics and coil springs;Bell;Angle Orthod,1951
5. Some facts concerning the open coil spring;Born;Am J Orthod,1955