@article{SF_1977__14_186359,
     author = {T. Head},
     title = {An algebraic characterization of multiplicative semigroups of real valued functions.},
     journal = {Semigroup forum},
     pages = {93--94},
     publisher = {mathdoc},
     volume = {14},
     year = {1977},
     zbl = {0359.20058},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__14_186359/}
}