@article{kachi_mukai, 
  title={The 19 and 20-th Homotopy Groups of the Rotation Groups R<sub>n</sub>}, 
  volume={42}, 
  DOI={10.18926/mjou/33289}, 
  number={1}, 
  publisher={Department of Mathematics, Faculty of Science, Okayama University}, 
  author={Kachi, Hideyuki and Mukai, Juno}
  }