1. Angle EH. Malocclusion of the teeth. Philadelphia: S.S. White Dental Mfg. Co. 1907:35–59.
2. Ballard CF. The significance of the soft tissue morphology in diagnosis, prognosis and treatment planning. Trans Eur Orthod Soc 1953;143–75.
3. Ballard CF. Morphology and treatment of Class II, division 2 occlusions. Trans Eur Orthod Soc 1956;44–54.
4. Binda SKR et al. A long-term cephalometric evaluation of treated Class II division 2 malocclusions. Eur J Orthod 1994;16:301–8.
5. Dahlberg G. Statistical methods for medical and biological students. New York: Interscience Publications, 1940.