@article{Ulrich:2016oO,
  author = "Ulrich, Ralf Matthias",
  title = "{Extension of the measurement of the proton-air cross section with the Pierre Auger Observatory }",
  doi = "10.22323/1.236.0401",
  journal = "PoS",
  year = 2016,
  volume = "ICRC2015",
  pages = "401"
}