@misc{indiciae25851743be93,
  title = {The Dirac Equation and Conditional Invariants.},
  author = {G Y Rainich},
  year = {1941},
  doi = {10.1073/pnas.27.7.355},
  url = {https://pubmed.ncbi.nlm.nih.gov/16578019/},
  note = {Source identifier: 16578019}
}