Indexed counter languages

Duske, J.; Middendorf, M.; Parchmann, R.

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Volume 26 (1992) p. 93-113

The structure of index sets and reduced indexed grammars

Parchmann, R.; Duske, J.

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications, Volume 24 (1990) p. 89-104