@misc{indiciae6e0e9ed0b4ea,
  title = {A large bubble around the Crab Nebula},
  author = {Romani, Roger W. and Reach, William T. and Koo, Bon Chul and Heiles, Carl},
  year = {1990},
  url = {https://ntrs.nasa.gov/citations/19900037457},
  note = {Source identifier: 19900037457}
}