Construction of minimal non-invertible skew-product maps on 2-manifolds
  Applying the Hric-J\"ager blow up technique, we give an affirmative answer to the question about the existence of non-invertible minimal circle-fibered self-maps of the Klein bottle. In addition, we present a simpler construction of a non-invertible minimal self-map of two dimensional torus. 
Jakub \v{S}otola and Sergei Trofimchuk
math.DS