1. Traumatic Injuries of the Teeth;Andreasen,1972
2. Textbook of Dental Anatomy and Physiology;Wheeler,1965
3. Clinical Endodontics;Sommer,1966
4. Endodontic Therapy;Weine,1976
5. the Prognosis of Pulp and Root Canal Therapy;Grahnen;Odontol. Revy,1961