@article{Czakon:2008Np,
  author = "Czakon, Michael",
  title = "{Mass effects and four-particle amplitudes at the two-loop level in QCD}",
  doi = "10.22323/1.048.0026",
  journal = "PoS",
  year = 2008,
  volume = "RAD COR 2007",
  pages = "026"
}