@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/