@misc{indiciae9fa73c3f1047,
  title = {On Monothetic Groups.},
  author = {P R Halmos and H Samelson},
  year = {1942},
  doi = {10.1073/pnas.28.6.254},
  url = {https://pubmed.ncbi.nlm.nih.gov/16578045/},
  note = {Source identifier: 16578045}
}