@article{10_1090_S0894_0347_1991_1080112_5,
     author = {Mather, John N.},
     title = {Variational construction of orbits of twist diffeomorphisms},
     journal = {Journal of the American Mathematical Society},
     pages = {207--263},
     publisher = {mathdoc},
     volume = {04},
     number = {2},
     year = {1991},
     doi = {10.1090/S0894-0347-1991-1080112-5},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-1991-1080112-5/}
}