@misc{indiciae8f96b2e1371b,
  title = {Differentiable pseudo-free circle actions.},
  author = {D Montgomery and C T Yang},
  year = {1971},
  doi = {10.1073/pnas.68.5.894},
  url = {https://pubmed.ncbi.nlm.nih.gov/16591917/},
  note = {Source identifier: 16591917}
}