@article{MS2_1985__56_166930,
     author = {O.A. Laudal and A. Sletsjoe},
     title = {Betti numbers of monoid algebras. {Applications} to 2-dimensional torus imbeddings.},
     journal = {Mathematica Scandinavica},
     pages = {145--162},
     publisher = {mathdoc},
     volume = {56},
     year = {1985},
     zbl = {0594.13010},
     url = {http://geodesic.mathdoc.fr/item/MS2_1985__56_166930/}
}