  The classical Poincar{\'e} conjecture that every homotopy 3-sphere is
diffeomorphic to the 3-sphere is proved by G. Perelman by solving Thurston's
program on geometrizations of 3-manifolds. A new confirmation of this
conjecture is given by combining R. H. Bing's result on this conjecture with
Smooth Unknotting Conjecutre for an $S^2$-knot and Smooth 4D Poincar{\'e}
Conjecture.
