@article{MM2_1991__71_3_155606,
     author = {J. KNOPFMACHER and K.-H. Indlekofer and R. Warlimont},
     title = {Arithmetical semigroups {I:} direct factors.},
     journal = {Manuscripta mathematica},
     pages = {83--96},
     publisher = {mathdoc},
     volume = {71},
     number = {3},
     year = {1991},
     zbl = {0723.11048},
     url = {http://geodesic.mathdoc.fr/item/MM2_1991__71_3_155606/}
}