@article{NUMA_1992__62_1_133639,
     author = {H.J.C. Barbosa and Thomas J.R. Hughes},
     title = {Boundary {Lagrange} multipliers in finite element methods: error analysis in natural forms.},
     journal = {Numerische Mathematik},
     pages = {1--16},
     year = {1992},
     volume = {62},
     number = {1},
     zbl = {0765.65102},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1992__62_1_133639/}
}