Max Rabkin. Ogden's Lemma for ET0L Languages. In Adrian Horia Dediu, Carlos Martín-Vide, editors, Language and Automata Theory and Applications - 6th International Conference, LATA 2012, A Coruña, Spain, March 5-9, 2012. Proceedings. Volume 7183 of Lecture Notes in Computer Science, pages 458-467, Springer, 2012. [doi]
Abstract is missing.