@misc{indiciae628c51a7a2f0,
  title = {Characteristic Coordinates for Hyperbolic Differential Equations in the Large.},
  author = {T Y Thomas},
  year = {1947},
  doi = {10.1073/pnas.33.8.242},
  url = {https://pubmed.ncbi.nlm.nih.gov/16578268/},
  note = {Source identifier: 16578268}
}