@article{SF_1989__39_2_134995,
     author = {M. Gass},
     title = {An order topology for finitely generated free monoids.},
     journal = {Semigroup forum},
     pages = {335--346},
     publisher = {mathdoc},
     volume = {39},
     number = {2},
     year = {1989},
     zbl = {0682.06012},
     url = {http://geodesic.mathdoc.fr/item/SF_1989__39_2_134995/}
}