@article{GDZPPN001254049, title = {Generalized Greenfs theories.}, journal = {Semigroup forum}, volume = {20}, year = {1980}, pages = {95-128}, zbl = {0438.20045}, url = {http://dml.mathdoc.fr/item/GDZPPN001254049} }
Carruth, J.H.; Clark, C.E. Generalized Greenfs theories.. Semigroup forum, Tome 20 (1980) pp. 95-128. http://gdmltest.u-ga.fr/item/GDZPPN001254049/