Quaternion-Kahler spaces, hyperkahler cones, and the c-map
  Under the action of the c-map, special Kahler manifolds are mapped into a class of quaternion-Kahler spaces. We explicitly construct the corresponding Swann bundle or hyperkahler cone, and determine the hyperkahler potential in terms of the prepotential of the special Kahler geometry. 
Martin Rocek, Cumrun Vafa, and Stefan Vandoren