Free symmetric group algebras in division rings generated by   poly-orderable groups
  We show that the canonical involution on a nonabelian poly-orderable group G extends to the Hughes-free division ring of fractions D of the group algebra k[G] of G over a field k and that, with respect to this involution, D contains a pair of symmetric elements freely generating a free group subalgebra of D over k. 
Vitor O. Ferreira, Jairo Z. Goncalves, Javier Sanchez
math.RA