@Article{LoeLuSe-JLAP-07,
  author = 	 {C. L\"oding and C. Lutz and O. Serre},
  title = 	 {Propositional Dynamic Logic with Recursive Programs},
  journal = 	 {Journal of Logic and Algebraic Programming},
  year = 	 {2007},
  volume =       {73},
  pages =        {51--69}
}