It has since been elaborated by Freedman, Robert Gompf, Clifford Taubes and Laurence Taylor to show there exists a continuum of non-diffeomorphic smooth structures on R4.
Utána Freedman, Robert Gompf, Clifford Taubes és Laurence Taylor mutatta meg, hogy kontinuum sok nem-diffeomorf sima struktúra létezik R4-en.