@article{GDZPPN001257722, title = {Semilattices which must contain a copy of 2 N.}, journal = {Semigroup forum}, volume = {31}, year = {1985}, pages = {71-78}, zbl = {0564.06003}, url = {http://dml.mathdoc.fr/item/GDZPPN001257722} }
Lawson, J.D.; Mislove, M. Semilattices which must contain a copy of 2 N.. Semigroup forum, Tome 31 (1985) pp. 71-78. http://gdmltest.u-ga.fr/item/GDZPPN001257722/