@techreport{SchielaWollner2008, author = {Anton Schiela and Winnifried Wollner}, title = {Barrier Methods for Optimal Control Problems with Convex Nonlinear Gradient Constraints}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {08-47}, language = {eng}, year = {2008} }