James N. Gray, Michael A. Harrison, and Oscar H. Ibarra. Two-way pushdown automata. J. E. Hopcroft and J. D. Ullman. Decidable and undecidable questions about automata. J. E. Hopcroft and J. D. Ullman.
Sets accepted by one-way stack automata are context sensitive.
Donald E. Knuth and Richard H. Bigelow. Programming language for automata. Two-type bracketed grammars.