@misc{indiciae661d7b8c0733,
  title = {Vector Fields on the n-Sphere.},
  author = {N E Steenrod and J H Whitehead},
  year = {1951},
  doi = {10.1073/pnas.37.1.58},
  url = {https://pubmed.ncbi.nlm.nih.gov/16588991/},
  note = {Source identifier: 16588991}
}