@inproceedings{Usoskin:2021nK,
  author = "Usoskin, Ilya  and  Koldobskiy, Sergey  and  Kovaltsov, Gennady  and  Sukhodolov, Timofei  and  Mishev, Alexander  and  Mironova, Irina",
  title = "{Strongest directly observed Solar Proton Event of 23-Feb-1956: Revised reference for the cosmogenic-isotope method}",
  doi = "10.22323/1.395.1319",
  booktitle = "Proceedings of 37th International Cosmic Ray Conference {\textemdash} PoS(ICRC2021)",
  year = 2021,
  volume = "395",
  pages = "1319"
}