TY  - RPRT
TI  - Diminished radiographic contrast between calculus and dentin.
AU  - D E Clark
AU  - S S Appleton
PY  - 1991
DO  - 10.1016/0030-4220(91)90208-t
UR  - https://pubmed.ncbi.nlm.nih.gov/1891235/
ID  - 1891235
ER  -