Freeness, linear disjointness, and implicitization -- a classical approach. Steinwandt, Rainer, Müller-Quade, Jörn (2000) Beiträge zur Algebra und Geometrie
Fuzzy subfields. Volf, Aurelian Claudiu (2001) Analele Ştiinţifice ale Universităţii “Ovidius" Constanţa. Seria: Matematică