@article{GDZPPN00247624X, title = {Pre-fields and Universal Algebraic Extensions; Equational Precessions.}, journal = {Monatshefte f\"ur Mathematik}, volume = {72}, year = {1968}, pages = {315-324}, zbl = {0162.32503}, url = {http://dml.mathdoc.fr/item/GDZPPN00247624X} }
Foster, Alfred L. Pre-fields and Universal Algebraic Extensions; Equational Precessions.. Monatshefte für Mathematik, Tome 72 (1968) pp. 315-324. http://gdmltest.u-ga.fr/item/GDZPPN00247624X/