@article{SEMR_2007_4_a1,
     author = {A. E. Frid},
     title = {Canonical decomposition of catenation of factorial languages},
     journal = {Sibirskie \`elektronnye matemati\v{c}eskie izvesti\^a},
     pages = {12--19},
     publisher = {mathdoc},
     volume = {4},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SEMR_2007_4_a1/}
}