@article{10_4153_CJM_1977_055_6,
     author = {Clarke, Frank H.},
     title = {Inequality {Constraints} in the {Calculus} of {Variations}},
     journal = {Canadian journal of mathematics},
     pages = {528--540},
     year = {1977},
     volume = {29},
     number = {3},
     doi = {10.4153/CJM-1977-055-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1977-055-6/}
}