@article{ELA_2011__22__a33,
     author = {Kunkel, Peter and Mehrmann, Volker},
     title = {Formal adjoints of linear {DAE} operators and their role in optimal control},
     journal = {The electronic journal of linear algebra},
     pages = {672--693},
     publisher = {mathdoc},
     volume = {22},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ELA_2011__22__a33/}
}