Necessary conditions for some optimal control problem for a nonlinear 2-D system are considered. These conditions can be obtained in the form of a quasimaximum principle.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-am29-2-8, author = {Barbara Bily}, title = {Optimal control for 2-D nonlinear control systems}, journal = {Applicationes Mathematicae}, volume = {29}, year = {2002}, pages = {239-249}, zbl = {1038.93046}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-am29-2-8} }
Barbara Bily. Optimal control for 2-D nonlinear control systems. Applicationes Mathematicae, Tome 29 (2002) pp. 239-249. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-am29-2-8/