New coordinates are given which describe non-degenerate Kerr black holes in
dual-null foliations based on the outer (or inner) horizons, generalizing the
Kruskal form for Schwarzschild black holes. The construction involves an area
radius for the transverse surfaces and a generalization of the Regge-Wheeler
radial function, both functions of the original radial coordinate only.Comment: 4 revtex4 page