9Neo J, Chee LF. A retrospective clinical study of endodontically treated mandibular incisors in a selected Chinese population. Oral Surg Oral Med Oral Pathol, 1990, 70:782-783.
10Bellizzi R, Hartwell G. Clinical investigation of in vivo endodontically treated mandibular anterior teeth. J Endod, 1983, 9 :246-248.