@misc{indiciae1f848a994b11,
  title = {Optimal trajectories between Earth and Mars in their true planetary orbits.},
  author = {Gravier, J. P. and Marchal, C. and Culp, R. D.},
  year = {1972},
  url = {https://ntrs.nasa.gov/citations/19720036158},
  note = {Source identifier: 19720036158}
}