@inproceedings{Usoskin:201785, author = "Usoskin, Ilya and Asvestari, Eleanna and Willamo, Teemu and Gil, Agnieszka and Kovaltsov, Gennady and Mikhailov, Vladimir and Mayorov, Andrey", title = "{Analysis of Ground-Level Enhancements: Strong events are hard}", doi = "10.22323/1.301.0126", booktitle = "Proceedings of 35th International Cosmic Ray Conference {\textemdash} PoS(ICRC2017)", year = 2017, volume = "301", pages = "126" }