Kustaanheimo-Stiefel transformation and static zero modes of Dirac   operator
  By exploiting the relation between static zero modes of massless Dirac operator and Kustaanheimo-Stiefel (Hopf) bundle sections, a general zero modes Ansatz which depends on an arbitrary real vector-function on $R^3$ is constructed. 
D.V. Aleynikov, E.A. Tolkachev