1. E. Bierstone, Lifting isotopies from orbit spaces, Topology, (1975), 245–252.
2. G. Bredon, Transformation groups on spheres with two types of orbits, Topology, 3 (1965), 103–113.
3. _____, Introduction to Compact Transformation Groups, Academic Press, New York, 1972.
4. _____, Biaxial actions, mimeographed notes, Rutgers University, 1973.
5. W. Browder and F. Quinn, A surgery theory for G-manifolds and stratified sets, Manifolds, University of Tokyo Press, 1973, 27–36.