@misc{indiciae03cb2b2020b9,
  title = {Classical geometries defined by exterior differential systems on higher frame bundles},
  author = {Estabrook, Frank B. and Wahlquist, Hugo D.},
  year = {1989},
  url = {https://ntrs.nasa.gov/citations/19890056218},
  note = {Source identifier: 19890056218}
}