Voir la notice de l'article provenant de la source Theory and Applications of Categories website
A pregroup is a partially ordered monoid in which every element has a left and a right adjoint. The main result is that for some well-behaved subgroups of the group of diffeomorphisms of the real numbers, the set of all endofunctions of the integers that are asymptotic at $\pm\infty$ to (the restriction to the integers of) a function in the subgroup is a pregroup.
@article{TAC_2004_12_a7, author = {Michael Barr}, title = {On subgroups of the {Lambek} pregroup}, journal = {Theory and applications of categories}, pages = {262--269}, publisher = {mathdoc}, volume = {12}, year = {2004}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2004_12_a7/} }
Michael Barr. On subgroups of the Lambek pregroup. Theory and applications of categories, Tome 12 (2004), pp. 262-269. http://geodesic.mathdoc.fr/item/TAC_2004_12_a7/