@misc{indiciae16ee1a3e3db9,
  title = {Diminished radiographic contrast between calculus and dentin.},
  author = {D E Clark and S S Appleton},
  year = {1991},
  doi = {10.1016/0030-4220(91)90208-t},
  url = {https://pubmed.ncbi.nlm.nih.gov/1891235/},
  note = {Source identifier: 1891235}
}