@article{SF_1990__41_2_135032,
     author = {J. N\'eraud},
     title = {On the deficit of a set of words.},
     journal = {Semigroup forum},
     pages = {1--22},
     publisher = {mathdoc},
     volume = {41},
     number = {2},
     year = {1990},
     zbl = {0679.20049},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__41_2_135032/}
}