Makoto Kanazawa. Ogden's lemma, multiple context-free grammars, and the control language hierarchy. Inf. Comput., 269, 2019. [doi]
@article{Kanazawa19-0, title = {Ogden's lemma, multiple context-free grammars, and the control language hierarchy}, author = {Makoto Kanazawa}, year = {2019}, doi = {10.1016/j.ic.2019.104449}, url = {https://doi.org/10.1016/j.ic.2019.104449}, researchr = {https://researchr.org/publication/Kanazawa19-0}, cites = {0}, citedby = {0}, journal = {Inf. Comput.}, volume = {269}, }