@misc{indiciae9cb63b6e0a09,
  title = {Linear and regular celestial mechanics- Perturbed two-body motion, numerical methods, canonical theory},
  author = {Scheifele, G. and Stiefel, E. L.},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19710053774},
  note = {Source identifier: 19710053774}
}