@article{HoefnerMoellerSolin2006,
  author    = {Peter H{\"o}fner and Bernhard M{\"o}ller and Kim Solin},
  title     = {Omega algebra, demonic refinement algebra and commands},
  journal   = {Lecture Notes in Computer Science},
  volume    = {4136},
  pages     = {222 -- 234},
  doi       = {10.1007/11828563_15},
  year      = {2006},
}