1. Principles of tribology;Halling,1975
2. Friction. An introduction to tribology;Bowden,1973
3. Friction and wear of materials;Rabinowicz,1965
4. Frictional forces in fixed orthodontic appliance;Nicolls;Dent Practit,1968
5. A comparitive study of frictional resistances between orthodontic bracket and archwire;Frank;AM J ORTHOD,1980