@article{ITA_1981__15_2_161_0, author = {Ehrenfeucht, A. and Rozenberg, G.}, title = {FPOL systems generating counting languages}, journal = {RAIRO. Informatique th\'eorique}, pages = {161--173}, publisher = {EDP-Sciences}, volume = {15}, number = {2}, year = {1981}, zbl = {0469.68077}, mrnumber = {618453}, language = {en}, url = {http://archive.numdam.org/item/ITA_1981__15_2_161_0/} }