@article{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",
  journal = "PoS",
  year = 2021,
  volume = "ICRC2021",
  pages = "1319"
}