@article{00874389, title = {The theory of }, journal = {Portugaliae Mathematica. Nova S\'erie}, volume = {53}, year = {1996}, pages = {1-22}, zbl = {0849.28002}, language = {en}, url = {http://dml.mathdoc.fr/item/00874389} }
Lintz, R.G. The theory of . Portugaliae Mathematica. Nova Série, Tome 53 (1996) pp. 1-22. http://gdmltest.u-ga.fr/item/00874389/