@article{GDZPPN001261622,
title = {Semigroup structures on \ss N.},
journal = {Semigroup forum},
volume = {44},
year = {1992},
pages = {238-244},
zbl = {0746.22002},
url = {http://dml.mathdoc.fr/item/GDZPPN001261622}
}
Strauss, D. Semigroup structures on ßN.. Semigroup forum, Tome 44 (1992) pp. 238-244. http://gdmltest.u-ga.fr/item/GDZPPN001261622/