Discrete constant mean curvature nets in space forms: Steiner's formula   and Christoffel duality
  We show that the discrete principal nets in quadrics of constant curvature that have constant mixed area mean curvature can be characterized by the existence of a K\"onigs dual in a concentric quadric. 
A. Bobenko, U. Hertrich-Jeromin, I. Lukyanenko
math.DG