M. Gugat, M. Herty, A. Klar, G. Leugering, and V. Schleper. Constrained optimization and optimal control for partial differential equations, volume 160 of International series of numerical mathematics, page 123-146. Birkhäuser, (2012)
V. Schleper, M. Gugat, M. Herty, A. Klar, and G. Leugering. Constrained Optimization and Optimal Control for Partial Differential
Equations, volume 160 of International Series of Numerical Mathematics, Birkh�user, (2012)