@misc{indiciae4976c54857b4,
  title = {A Theorem on Extremals: I.},
  author = {S Lefschetz},
  year = {1935},
  doi = {10.1073/pnas.21.5.272},
  url = {https://pubmed.ncbi.nlm.nih.gov/16577670/},
  note = {Source identifier: 16577670}
}