@article{Boels:2016lw,
  author = "Boels, Rutger  and  Kniehl, Bernd  and  Yang, Gang",
  title = "{Towards a four loop form factor}",
  doi = "10.22323/1.235.0110",
  journal = "PoS",
  year = 2016,
  volume = "RADCOR2015",
  pages = "110"
}