@article{NUMA_1977__28_132496,
     author = {F. Brezzi and W.W. Hager and P.A. Raviart},
     title = {Error {Estimates} for the {Finite} {Element} {Solution} of {Variational} {Inequalities.} {Part} {I.} {Primal} {Theory.}},
     journal = {Numerische Mathematik},
     pages = {431--444},
     publisher = {mathdoc},
     volume = {28},
     year = {1977},
     zbl = {0369.65030},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1977__28_132496/}
}