[2] Novotný M.: On a class of contextual grammars. Cahieгs de linguistique théorique et appliquée 11 (1974), Fasc. 2, 313-314.
[3] Novotný M.: On muiticontextual grammars. (manuscгipt).
[4] Novotný M.: 
On some variants of contextual languages. Rеv. Roum. Math. Purеs еt Appl. 21 (1976), 1053-1062. 
MR 0428829[5] Novotný M.: 
Each generalized contextual language is context sensitive. Rеv. Roum. Math. Purеs еt Appl. 21 (1976), 353-362. 
MR 0405943 | 
Zbl 0333.68048[6] Ginsburg S.: 
The mathematical theory of context-free languages. Mc Graw Hill Book Company Nеw York, 1966.                                                             
MR 0211815 | 
Zbl 0184.28401[7] Pawlak Z.: 
Maszyny programowane. Algorytmy 10, volumе 5, 1969, 5-19. 
MR 0255104[8] Čulík K.: 
Some notes on finite state languages and events represented by finite automata using labelled graphs. Čas. pěst. mat, 86, 43-55 (1961). 
MR 0130062[9] Marcus S.: 
Gramatici şi automate finite. Editura acadеmiеi rеpublicii popularе Rominе, 1964. 
MR 0174411[10] Păun G.: 
On the smallest number of nonterminals required to generate a context-free language. Rеv. Anal. Numér. Théor. Approx. 18 (41), t. 2 (1976), 203-208. 
MR 0489052[11] Gruska J.: 
On a classification of context-free languages. Kybеrnеtika (Praguе) 3, Nr. 1 (1967), 22-29. 
MR 0209092 | 
Zbl 0158.25401[12] Gruska J.: 
Descriptional complexity of context-free languages. Mathеmatical Foundations of Computеr Sciеncе. Procееdings of Symposium and Summеr School. High Tatras, Sеptеmbег 3 to 8, 1973 (1973), 71-83. 
MR 0405938