@misc{indiciae5844b6ee4d00,
  title = {Classical Time Crystals},
  author = {Shapere, Alfred and Wilczek, Frank},
  year = {2012},
  doi = {10.1103/physrevlett.109.160402},
  url = {https://www.osti.gov/biblio/1101589},
  note = {Source identifier: 1101589}
}