@ARTICLE{CsuDasMitPau_j1993, author = {Erzs\'ebet~Csuhaj-Varj\'u and J{\"u}rgen~Dassow and Victor~Mitrana and Gheorghe~P\u{a}un}, title = {Cooperation in grammar systems: universality, similarity, timing}, journal = kyb, year = 1993, volume = 36, number = {}, pages = {271-286} }