@article{MZ_1973__135_171995,
     author = {S. Hildebrandt and H.C. Wente},
     title = {Variational {Problems} with {Obstacles} and a {Volume} {Constraint.}},
     journal = {Mathematische Zeitschrift},
     pages = {55--68},
     publisher = {mathdoc},
     volume = {135},
     year = {1973},
     zbl = {0284.49017},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__135_171995/}
}