Let D be a division ring with centre k. We show that D contains the k-
group algebra of the free group on two generators when D is the ring o
f fractions of a suitable skew polynomial ring, or it is generated by
a polycyclic-by-finite group which is not abelian-by-finite, or it is
the ring of fractions of the universal enveloping algebra of a finite-
dimensional Lie algebra of characteristic zero. (C) 1996 Academic Pres
s, Inc.