@misc{indiciae4023cc8d56a7,
  title = {Curvature Element Transformations Which Preserve Integrable Fields.},
  author = {E Kasner and J De Cicco},
  year = {1939},
  doi = {10.1073/pnas.25.2.104},
  url = {https://pubmed.ncbi.nlm.nih.gov/16588267/},
  note = {Source identifier: 16588267}
}