Duality transformation for 3+1 dimensional Yang-Mills theory
  Dual form of 3+1 dimensional Yang-Mills theory is obtained as another SO(3) gauge theory. Duality transformation is realized as a canonical transformation. The The non-abelian Gauss law implies the corresponding Gauss law for the dual theory. The dual theory is non-local. There is a non-local version of Yang-Mills theory which is self dual. 
Pushan Majumdar, H.S.Sharatchandra