@ARTICLE{DasMas_j2012, author = {J{\"u}rgen~Dassow and Tom\'a\v{s}~Masopust}, title = {On restricted context-free grammars}, journal = jcss, year = 2012, volume = {78}, number = {1}, pages = {293--304}, url = {http://dx.doi.org/10.1016/j.jcss.2011.05.008} }