@article{SF_1974__6_133977,
     author = {G. Thierrin},
     title = {The syntactic monoid of a hypercode.},
     journal = {Semigroup forum},
     pages = {227--231},
     year = {1974},
     volume = {6},
     zbl = {0262.20086},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__6_133977/}
}