1. Indexed grammars—An extension of context-free grammars;Aho;J. Assoc. Comp. Mach.,1968
2. Infinite chains of hyper-AFL's;Asveld,1975
3. Reversal-bounded multipushdown machines;Baker;J. Comp. System Sci.,1974
4. Hyper-AFL's and ETOL Systems;Christensen,1974
5. Hyper-AFL's and ETOL Systems;Christensen,1974