@article{ITA_1990__24_1_89_0,
     author = {Parchmann, R. and Duske, J.},
     title = {The structure of index sets and reduced indexed grammars},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {89--104},
     publisher = {EDP-Sciences},
     volume = {24},
     number = {1},
     year = {1990},
     mrnumber = {1060468},
     zbl = {0701.68071},
     language = {en},
     url = {http://archive.numdam.org/item/ITA_1990__24_1_89_0/}
}