His first major contribution (in collaboration with F Hirzebruch) was the development of a new and powerful technique in topology (K-theory) which led to the solution of many outstanding difficult problems.
Kanyang unang malaking kontribusyon (sa pakikipagtulungan sa F Hirzebruch) ay ang pagbuo ng isang bago at malakas na pamamaraan sa topology (K-theory) na humantong sa ang solusyon ng maraming mga outstanding na problema.