@misc{indiciae78b1c64c0707,
  title = {Chemical evolution of dense clouds},
  author = {Chappelle, E. W. and Donn, B. D. and Payne, W. A., Jr. and Stief, L. J.},
  year = {1972},
  url = {https://ntrs.nasa.gov/citations/19720022480},
  note = {Source identifier: 19720022480}
}