@misc{indiciae06380aa1105e,
  title = {Transformations Preserving the Tetrad Equations.},
  author = {E B Wilson},
  year = {1933},
  doi = {10.1073/pnas.19.10.882},
  url = {https://pubmed.ncbi.nlm.nih.gov/16587804/},
  note = {Source identifier: 16587804}
}