@ARTICLE{CFL11,
  author      = {Wojciech Czerwi{\'n}ski and Sibylle Fr{\"o}schle and S{\l}awomir Lasota},
  TITLE = {Partially-commutative context-free processes: expressibility and tractability},
  JOURNAL = {Information and Computation},
  YEAR = {2011},
  VOLUME = {209},
  NUMBER = {},
  PAGES = {782-798}
}