@article{GDZPPN001258656, title = {On numerical semigroups.}, journal = {Semigroup forum}, volume = {33}, year = {1986}, pages = {63-84}, zbl = {0614.10046}, url = {http://dml.mathdoc.fr/item/GDZPPN001258656} }
Häggkvist, R.; Fröberg, R.; Gottlieb, C. On numerical semigroups.. Semigroup forum, Tome 33 (1986) pp. 63-84. http://gdmltest.u-ga.fr/item/GDZPPN001258656/