@article{EP_2003_13_a2,
     author = {E. Casas and Mariano Mateos and Fredi Tr\"oltzsch},
     title = {Necessary and {Sufficient} {Optimality} {Conditions} for {Optimization} {Problems} in {Function} {Spaces} and {Applications} to {Control} {Theory}},
     journal = {ESAIM. Proceedings},
     pages = {18--30},
     publisher = {mathdoc},
     volume = {13},
     year = {2003},
     doi = {10.1051/proc:2003001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1051/proc:2003001/}
}