@misc{indiciae45bc4c6f8ed3,
  title = {ABSTRACT HOMOTOPY. IV.},
  author = {D M Kan},
  year = {1956},
  doi = {10.1073/pnas.42.8.542},
  url = {https://pubmed.ncbi.nlm.nih.gov/16589902/},
  note = {Source identifier: 16589902}
}