Ira Neitzel Thomas Wick Winnifried Wollner An Optimal Control Problem Governed by a Regularized Phase-Field Fracture Propagation Model. 2271-2288 2017 55 SIAM J. Control. Optim. 4 https://doi.org/10.1137/16M1062375 db/journals/siamco/siamco55.html#NeitzelWW17