@article{ITA_2012__46_3_355_0,
     author = {Cassaigne, Julien and Nicolas, Francois},
     title = {On the decidability of semigroup freeness},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {355--399},
     publisher = {EDP-Sciences},
     volume = {46},
     number = {3},
     year = {2012},
     doi = {10.1051/ita/2012010},
     mrnumber = {2981675},
     zbl = {1252.20050},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1051/ita/2012010/}
}