@article{10_4153_CJM_1980_039_9,
     author = {Clarke, Frank H.},
     title = {The {Erdmann} {Condition} and {Hamiltonian} {Inclusions} in {Optimal} {Control} and the {Calculus} of {Variations}},
     journal = {Canadian journal of mathematics},
     pages = {494--509},
     year = {1980},
     volume = {32},
     number = {2},
     doi = {10.4153/CJM-1980-039-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1980-039-9/}
}