1. Gruska (1967) and (1969) are basic papers on the syntactic complexity of context-free languages. A summary of the results in this field is given in Gruska (1973) and Kelemenova (1982). Further new results can be found in Blum (1983), Bucher (1981), Gabow (1984).
2. The first paper on the syntactic complexity of matrix and programmed grammars is Cremers . (1979). It contains very weak comparison results concerning Var and Prod1 and the independence of these measures and Mat (Theorem 4.3.3).
3. A detailed study of the nonterminal complexity with respect to some regulated grammars is presented in Dassow (1984-b), PĂUn (1984-b), Dassow and PĂUn (1985-a) and (1986-b). The Sections 4.1 and 4.2. are based on these references.
4. In the paper by Bucher . (1981) the complexity of finite languages with respect to the number of productions and some classes of grammars is studied. Programmed grammars are also taken into consideration. Essentially, Lemma 4.3.3 is given there. Lemma 4.3.4 is contained in Dassow and PĂUn (1986).
5. Some material on the syntactic complexity can also be found in the monograph by PĂUn (1981-f). Dassow (1985-a) and Dassow and PĂUn (1984-b) give summaries of some results without proofs.