[1] Novotný M.: On a class of languages. Archivum Matematicum Brno 6 (1970), 155-170. MR 0319421

[2] Novotný M.: Algebraic structures of mathematical linguistics. Bull. Math. de la Soc. Sci. Math. de la R. S. de Roumanie 12 (60) (1969), 87-101. MR 0265086

[3] Gladkij A. V.: Konfiguracionnyje charakteristiki jazykov. Problemy kibernetiki 10 (1963), 251-260. MR 0184815

[4] Ginsburg S.: The mathematical theory of context-free languages. McGraw Hill Book Company 1966. MR 0211815 | Zbl 0184.28401

[5] Chomsky N.: On certain formal properties of grammars. Information and Control 2 (1959), 137-167. MR 0105365 | Zbl 0161.00804

[6] Novotný M.: On configurations in the sense of Kulagina. Publ. Fac. Sci. Univ. J. E. Purkyně Brno No 507 (1969), 301-316. MR 0280307