1. Extraoral force-facts and fallacies;Graber;Am J Orthod,1955
2. Mechanical principles in extraoral anchorage;Gould;Am J Orthod,1857
3. An evaluation of cervical traction on the maxilla and the upper first permanent molar;Klein;Angle Orthod,1957
4. Some observations on extraoral treatment;Newcomb;Angle Orthod,1958
5. Evaluation of cervical anchorage force in treatment;Kloehn;Angle Orthod,1961