@article{Emmanoulopoulos:2009Ur,
  author = "Emmanoulopoulos, Dimitrios",
  title = "{The nonlinear long term X ray variability of Mrk 421}",
  doi = "10.22323/1.063.0038",
  journal = "PoS",
  year = 2009,
  volume = "BLAZARS2008",
  pages = "038"
}