@article{GDZPPN001260456, title = {On the deficit of a set of words.}, journal = {Semigroup forum}, volume = {40}, year = {1990}, pages = {1-22}, zbl = {0679.20049}, url = {http://dml.mathdoc.fr/item/GDZPPN001260456} }
Néraud, J. On the deficit of a set of words.. Semigroup forum, Tome 40 (1990) pp. 1-22. http://gdmltest.u-ga.fr/item/GDZPPN001260456/