1. Anderson, G. M., Practical Orthodontics, 7. Aufl. St. Louis 1948.
2. Angle, E. H., Malocclusion of the Teeth. Philadelphia 1907.
3. Broekman, R. W., Schweiz. Mschr. Zahnheilk. (1966) 551.
4. Case, C. S., Amer. J. Orthodont.9 (1964) 559. (Repr. Trans NDA 1911).
5. Dewel, B. F. A Critical Analysis of Serial Extraction in Orthodontic Treatment. Amer. J. Orthodont.1959, 424;1954, 906.