@article{SF_1986__35_134857,
     author = {R. H\"aggkvist and R. Fr\"oberg and C. Gottlieb},
     title = {On numerical semigroups.},
     journal = {Semigroup forum},
     pages = {63--84},
     publisher = {mathdoc},
     volume = {35},
     year = {1986},
     zbl = {0614.10046},
     url = {http://geodesic.mathdoc.fr/item/SF_1986__35_134857/}
}