1. Context free grammars and pushdown storage;Chomsky,1962
2. The Mathematical Theory of Context Free Languages;Ginsburg,1966
3. Deterministic context free languages;Ginsburg;SDC Document No. TM-738/014/00,1965
4. Operations which preserve definability in languages;Ginsburg;J. Assoc. Computing Machinery,1965
5. Inverses of phrase structure generators;Greibach,1963