Max Gunzburger Hyung-Chun Lee A penalty/least-squares method for optimal control problems for first-order elliptic systems. 57-75 2000 107 Applied Mathematics and Computation 1 http://dx.doi.org/10.1016/S0096-3003(99)00010-7 db/journals/amc/amc107.html#GunzburgerL00