@article{GDZPPN001253565, title = {The structure of an idempotent relation.}, journal = {Semigroup forum}, volume = {18}, year = {1979}, pages = {319-330}, zbl = {0424.04001}, url = {http://dml.mathdoc.fr/item/GDZPPN001253565} }
Norris, E.M. The structure of an idempotent relation.. Semigroup forum, Tome 18 (1979) pp. 319-330. http://gdmltest.u-ga.fr/item/GDZPPN001253565/