@article{SF_1979__18_134335,
     author = {D. Schweigert},
     title = {On semigroups of polynomial functions.},
     journal = {Semigroup forum},
     pages = {5--8},
     publisher = {mathdoc},
     volume = {18},
     year = {1979},
     zbl = {0415.08001},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__18_134335/}
}