@article{qualit09,
  author    = {Luca de Alfaro and
               Krishnendu Chatterjee and
               Marco Faella and
               Axel Legay},
  title     = {Qualitative Logics and Equivalences for Probabilistic Systems},
  journal   = {Logical Methods in Computer Science},
  volume    = {5},
  number    = {2},
  year      = {2009}
}