@article{SF_1985__31_134735,
     author = {T. Nordahl},
     title = {Residual finiteness in permutation varieties of semigroups.},
     journal = {Semigroup forum},
     pages = {33--46},
     publisher = {mathdoc},
     volume = {31},
     year = {1985},
     zbl = {0552.20041},
     url = {http://geodesic.mathdoc.fr/item/SF_1985__31_134735/}
}