@article{MZ_1977__156_172573,
     author = {Walter Schempp},
     title = {On {Functions} of {Positive} {Type} on {Commutative} {Monoids.}},
     journal = {Mathematische Zeitschrift},
     pages = {115--122},
     publisher = {mathdoc},
     volume = {156},
     year = {1977},
     zbl = {0367.22007},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__156_172573/}
}