@article{SF_1985__32_134785,
     author = {V. Gould},
     title = {The characterisation of monoids by properties of their  {S-systems.}},
     journal = {Semigroup forum},
     pages = {251--266},
     publisher = {mathdoc},
     volume = {32},
     year = {1985},
     zbl = {0571.20067},
     url = {http://geodesic.mathdoc.fr/item/SF_1985__32_134785/}
}