His methods were so sharp as to actually provide a complete classification of all compact simply connected topological 4-manifolds, yielding many previously unknown examples of such manifolds, and many previously unknown homeomorphisms between known manifolds.
Kanyang mga pamamaraan ay kaya matalim na talagang magbigay ng isang kumpletong pag-uuri ng lahat ng mga kasunduan simpleng connected topological 4-manifolds, masunurin maraming mga dati hindi kilalang mga halimbawa ng ganoong manifolds, at maraming mga dati hindi kilalang homeomorphisms sa pagitan ng mga kilalang manifolds.