Voir la notice de l'article provenant de la source Czech Digital Mathematics Library
@article{KYB_1978__14_6_a1, author = {P\u{a}un, Gheorghe}, title = {Two infinite hierarchies of languages defined by branching grammars}, journal = {Kybernetika}, pages = {--407}, publisher = {mathdoc}, volume = {14}, number = {6}, year = {1978}, mrnumber = {529192}, zbl = {0394.68052}, language = {en}, url = {http://geodesic.mathdoc.fr/item/KYB_1978__14_6_a1/} }
Păun, Gheorghe. Two infinite hierarchies of languages defined by branching grammars. Kybernetika, Tome 14 (1978) no. 6, p. 407. http://geodesic.mathdoc.fr/item/KYB_1978__14_6_a1/