Optimal concentration and time for citric acid to etch the dentin disc 
Yuan Pei-yan1, Xu Ping-ping1, Huang Jian-sheng1, He Jian-bo2, Zou Chang-qing2
Chinese Journal of Tissue Engineering Research . 2012, (16): 2959 -2963 .  DOI: 10.3969/j.issn.1673-8225.2012.16.026