@ARTICLE{Istrail1978a, author = {Istrail, Sorin}, title = {A problem about contextual grammars with choice}, journal = {Studii si Cercetari Matematice}, year = {1978}, volume = {30}, pages = {401--408}, number = {4}, owner = {Derek}, timestamp = {2012.05.08}, category = {Theory of Computation} }