@article{SF_1995__50_3_135374,
     author = {Z. Liu},
     title = {Monoids over which all regular left acts are flat.},
     journal = {Semigroup forum},
     pages = {135--140},
     publisher = {mathdoc},
     volume = {50},
     number = {3},
     year = {1995},
     zbl = {0827.20078},
     url = {http://geodesic.mathdoc.fr/item/SF_1995__50_3_135374/}
}