Completion of closed form solution set to optical flow equations

M. Subbarao and A. M. Waxman (1985) gave the closed-form solution to the nonlinear formulation of the motion and structure equation of Waxman and S. Ullman (1983). They gave a rigorous proof of the uniqueness of their closed-form optical flow solutions for planar surfaces in motion. However, they failed to consider one special case where the planar pitch parallel to the image plane was translating only in the Z direction. The authors give a separate closed-form solution for this special case, thus completing the solution set for optical flow equations