@inproceedings{Grzelak:201973,
  author = "Grzelak, Grzegorz",
  title = "{Measurement of the $\psi(2S)$ to $J/\psi$ cross section ratio in photoproduction with the ZEUS detector at HERA}",
  doi = "10.22323/1.340.0921",
  booktitle = "Proceedings of The 39th International Conference on High Energy Physics {\textemdash} PoS(ICHEP2018)",
  year = 2019,
  volume = "340",
  pages = "921"
}