Subelliptic biharmonic maps
  We study subelliptic biharmonic maps, i.e. smooth maps from a compact strictly pseudoconvex CR manifold M into a Riemannian manifold N which are critical points of a certain bienergy functional. We show that a map is subelliptic biharmonic if and only if its vertical lift to the (total space of the) canonical circle bundle is a biharmonic map with respect to the Fefferman metric. 
Sorin Dragomir, Stefano Montaldo
math.DG