TY  - RPRT
TI  - Vector Fields on the n-Sphere.
AU  - N E Steenrod
AU  - J H Whitehead
PY  - 1951
DO  - 10.1073/pnas.37.1.58
UR  - https://pubmed.ncbi.nlm.nih.gov/16588991/
ID  - 16588991
ER  -