@article{GuttmannMoeller2006,
  author    = {Walter Guttmann and Bernhard M{\"o}ller},
  title     = {Modal design algebra},
  journal   = {Lecture Notes in Computer Science},
  volume    = {4010},
  pages     = {236 -- 256},
  doi       = {10.1007/11768173_14},
  year      = {2006},
}