@misc{indiciae1956a9c18abf,
  title = {Ammonia abundances in four comets},
  author = {Wickoff, Susan and Tegler, Stephen C. and Engel, Lisa},
  year = {1991},
  url = {https://ntrs.nasa.gov/citations/19910040756},
  note = {Source identifier: 19910040756}
}