Kim E, Lee B, Chang H, Lee W, Hong C, Min K. Evaluation of the radiopacity and cytotoxicity of Portland cements containing bismuth oxide. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology. 2008 Jan;105(1):e54–7. doi: 10.1016/j.tripleo.2007.08.001.