TY  - JOUR
AU  - Jörgen Backelin
TI  - On the number of semigroups of natural numbers.
JO  - Mathematica Scandinavica
PY  - 1990
SP  - 197
EP  - 215
VL  - 66
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MS2_1990__66_1_167105/
ID  - MS2_1990__66_1_167105
ER  -