@article{CMH_1994__69_4_140338,
     author = {J. Langer and D. Singer},
     title = {Liouville integrability of geometric variational problems.},
     journal = {Commentarii mathematici Helvetici},
     pages = {272--280},
     publisher = {mathdoc},
     volume = {69},
     number = {4},
     year = {1994},
     zbl = {0819.58017},
     url = {http://geodesic.mathdoc.fr/item/CMH_1994__69_4_140338/}
}