1. 1. MK Hine. Review of dentistry . St. Louis: Mosby. 1966 : 169 .
2. 2. PR Langlais, SL Bricker, AJ Cottone, and BR Baker. Oral diagnosis. Oral medicine and treatment planning . Philadelphia: Saunders. 1984 : 179 -180 .
3. 3. JI Ingle, and JF Talntor: Endodontics . Philadelphia: Lea & Febiger. 1985 : 497 -98 .
4. 4. S Seltzer. Endodontology: biologic considerations in endodontic procedures . Philadelphia: Lea & Febiger, 1988 : 155 .
5. 5. NK Wood, and PW Goaz. Differential diagnosis of oral lesions . St. Louis: Mosby. 1975 : 201 .