4Kobayashi C, Soda H. New electronic canal measuring device based on the ratio method [J]. JEndo, 1994, 20(3) : 111 - 114.
5Meredith N, Gulabivala K. Electrical impedance measurements of root canal length [J]. Endo Dent Traum, 1997, 13:126 - 131.
6Aurelio JA, Nahmias Y, Gerstein H. A model for demonstration an electronic canal length measuring device [ J ]. J Endo, 1983,9 : 568 -569.
7Nahmias Y, Aurelio JA, Gerstein H. An in vitro model for evaluation of electronic root canal length measuring devices [ J ]. J Endo, 1987, 13(5): 209-214.
8Donnelly JC. A simplified model to demonstrate the operation of electronic root canal measuring device [ J]. J Endo, 1993, 19 ( 11 ) : 579 - 580.
9Czerw R J, Fulkerson MS, Donnelly JC. An in vitro test of a simplified model to demonstrate the operation of electronic root canal measuring devices [J]. J Endo, 1994, 20(12) : 605 -606.
10Vajrahaya L, Tepmongkol P. Accuracy of apex locator [ J ]. Endod Dent Traum, 1997, 13:180-182
