1. National Library of Medicine-Medical Subjects Headings MeSH 2016. Available at: https://www.nlm.nih.gov/mesh/MBrowser.html. Accessed June 21, 2016.
2. American Association of Endodontics. AAE Case Difficulty Assessment Form and Guidelines. Available at: http://www.aae.org/uploadedfiles/publications_and_research/guidelines_and_position_statements/2006casedifficultyassessmentformb_edited2010.pdf. Accessed June 21 2016.
3. Problem Solving in Endodontics;Gutmann,2006
4. Coronal leakage as a cause of failure in root canal therapy; a review;Saunders;Endod Dent Traumatol,1994
5. A prospective study of the factors affecting outcomes of nonsurgical root canal treatment: part 1: periapical health;Ng;Int Endod J,2011