WKB expansion for the angular momentum and the Kepler problem: from the torus quantization to the exact one

We calculate the WKB series for the angular momentum and the non–relativistic 3-dim Kepler problem. This is the first semiclassical treatment of the angular momentum for terms beyond the leading WKB approximation. We explain why the torus quantization (the leading WKB term) of the full problem is exact, even if the individual torus quantization of the angular momentum and of the radial Kepler problem separately is not exact. PACS numbers: 03.65.-w, 03.65.Ge, 03.65.Sq