1. KINGSLEY, as quoted by Reidel in Chapter 9, of Current Orthodontic Concepts and Techniques (T. M. Graber, Editor), Volume II Saunders, Philadelphia, 1969.
2. LUNDSTROM, Malocclusions of the teeth regarded as a problem in connection with the apical base. Int. J. Orthodont. II: 591 - 1109, 1925.
3. McCAULEY, D. R.: The cuspid and its function in retention. Amer. J. Orthodont. 30:196-205, 1944.
4. TWEED, C. H.: Indications for the extraction of teeth in orthodontic procedures, Amer. J. Orthodont 30: 405 - 428, 1944.
5. ROGERS, A. P.: As quoted by Reidel in Chapter 9 of Current Orthodontic Concepts and Techniques, (T. M. Graber, Editor), Volume II.