@article{SF_1990__40_1_135001,
     author = {J. Justin and G. Pirillo},
     title = {Infinite words and permutation properties.},
     journal = {Semigroup forum},
     pages = {13--22},
     publisher = {mathdoc},
     volume = {40},
     number = {1},
     year = {1990},
     zbl = {0681.20039},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__40_1_135001/}
}