Spherical T-duality II: An infinity of spherical T-duals for   non-principal SU(2)-bundles
  Recently we initiated the study of spherical T-duality for spacetimes that are principal SU(2)-bundles. In this paper, we extend spherical T-duality to spacetimes that are oriented non-principal SU(2)-bundles. There are several interesting new examples in this case and a new phenomenon appearing in the non-principal case is the existence of infinitely many spherical T-duals. 
Peter Bouwknegt, Jarah Evslin, Varghese Mathai
hep-th math.DG