@article{ITA_1979__13_1_19_0,
     author = {Jantzen, Matthias},
     title = {On the hierarchy of {Petri} net languages},
     journal = {RAIRO. Informatique th\'eorique},
     pages = {19--30},
     publisher = {EDP-Sciences},
     volume = {13},
     number = {1},
     year = {1979},
     mrnumber = {525455},
     zbl = {0404.68076},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1979__13_1_19_0/}
}