@article{Schaefer:2020Ks,
  author = "Schaefer, Wolfgang  and  Cisek, Anna  and  Babiarz, Izabela  and  Szczurek, Antoni",
  title = "{Production of $\chi_c(i) \chi_c(j)$ pairs in proton-proton collisions in $k_t$-factorization and collinear approaches}",
  doi = "10.22323/1.364.0468",
  journal = "PoS",
  year = 2020,
  volume = "EPS-HEP2019",
  pages = "468"
}