@article{SF_1991__42_3_135064,
     author = {F. Halter-Koch},
     title = {Arithmetical semigroups defined by congruences.},
     journal = {Semigroup forum},
     pages = {59--62},
     publisher = {mathdoc},
     volume = {42},
     number = {3},
     year = {1991},
     zbl = {0734.20027},
     url = {http://geodesic.mathdoc.fr/item/SF_1991__42_3_135064/}
}