@article{GDZPPN001255282, title = {The local theory of semigroups in nilpotent Lie groups.}, journal = {Semigroup forum}, volume = {23}, year = {1981}, pages = {343-358}, zbl = {0531.22002}, url = {http://dml.mathdoc.fr/item/GDZPPN001255282} }
Hofmann, K.H.; Lawson, J.D. The local theory of semigroups in nilpotent Lie groups.. Semigroup forum, Tome 23 (1981) pp. 343-358. http://gdmltest.u-ga.fr/item/GDZPPN001255282/