@Article{sacs09,
  author = 	 {A. Sokolova and Vink, E.P. de and H. Woracek},
  title = 	 {Coalgebraic Weak Bisimulation for Action-Type Systems},
  journal = 	 {Scientific Annals of Computer Science},
  volume = 	 {19},
  year = 	 {2009},
  pages = 	 {93--144}
}