1. 1. Proffit WR (1978) Equilibrium theory revisited: Factors
2. influencing position of the teeth. Angle Orthod 48: 175-186.
3. 2. Graber TM, Swain BF (1975) Current orthodontic concepts
4. and techniques. W.B. Saunders Company; 2nd edition.
5. 3. Proffit WR (1975) Muscle pressures and tooth position: North