1. Chomsky N (1956) Three models for the description of language. IRE Trans Inf Theory 2(3): 113–124.
2. Hopcroft J E, Ullman J D (1969) Formal languages and theit relation to Automata, Addison-Wesley, Reading, Mass.
3. Hopcroft J E, Ullman J D (2007) Introduction to Automata Theory, Languages and Computation. Addison-Wesley, Reading, Mass.
4. Knuth D E Trabb Pardo L (1977) Early development of programming languages. In Dekker M (ed) Encyclopedia of computer science and technology 7. Marcel Dekker, New York.
5. Ledgard H F (1971) Ten mini-languages; a study of topical issues in programming languages. Computing Surveys 3(3): 115–146.