@article{ITA_1994__28_3-4_221_0,
     author = {Salomaa, Kai and Wood, D. and Yu, Sheng},
     title = {Pumping and pushdown machines},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {221--232},
     publisher = {EDP-Sciences},
     volume = {28},
     number = {3-4},
     year = {1994},
     mrnumber = {1282445},
     zbl = {0883.68093},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1994__28_3-4_221_0/}
}