@article{ITA_1992__26_2_151_0,
     author = {Rupert, C. P.},
     title = {Crossability of cancellative {Kleene} semigroups},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {151--161},
     publisher = {EDP-Sciences},
     volume = {26},
     number = {2},
     year = {1992},
     mrnumber = {1166785},
     zbl = {0751.20052},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1992__26_2_151_0/}
}