@article{BAG_1985__19_138291,
     author = {Hubert Grassmann},
     title = {On characters and characteristic polynomials of transformation semigroups},
     journal = {Beitr\"age zur Algebra und Geometrie},
     pages = {51--58},
     publisher = {mathdoc},
     volume = {19},
     year = {1985},
     zbl = {0596.20057},
     url = {http://geodesic.mathdoc.fr/item/BAG_1985__19_138291/}
}