@inproceedings{Emmanoulopoulos:2009Ur, author = "Emmanoulopoulos, Dimitrios", title = "{The nonlinear long term X ray variability of Mrk 421}", doi = "10.22323/1.063.0038", booktitle = "Proceedings of Workshop on Blazar Variability across the Electromagnetic Spectrum {\textemdash} PoS(BLAZARS2008)", year = 2009, volume = "063", pages = "038" }