Equivalences of Smooth and Continuous Principal Bundles with   Infinite-Dimensional Structure Group
  Let K be a a Lie group, modeled on a locally convex space, and M a finite-dimensional paracompact manifold with corners. We show that each continuous principal K-bundle over M is continuously equivalent to a smooth one and that two smooth principal K-bundles over M which are continuously equivalent are also smoothly equivalent. In the concluding section, we relate our results to neighboring topics. 
Christoph M\"uller and Christoph Wockel