@misc{indiciae71632296ab34,
  title = {Levinson theorem for Dirac particles.},
  author = {ZQ Ma and GJ Ni},
  year = {1985},
  doi = {10.1103/physrevd.31.1482},
  url = {https://pubmed.ncbi.nlm.nih.gov/9955853/},
  note = {Source identifier: 9955853}
}