@article{10_4064_aa112_3_4,
     author = {Alfred Geroldinger and Franz Halter-Koch},
     title = {Congruence monoids},
     journal = {Acta Arithmetica},
     pages = {263--296},
     publisher = {mathdoc},
     volume = {112},
     number = {3},
     year = {2004},
     doi = {10.4064/aa112-3-4},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa112-3-4/}
}