Classical Poincar{\'e} conjecture via 4D topology

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 Conjecture for an $S^2$-link and Smooth 4D Poincar{\'e} Conjecture.