@article{SIGMA_2011_7_a41,
     author = {Thomas Curtright},
     title = {Potentials {Unbounded} {Below}},
     journal = {Symmetry, integrability and geometry: methods and applications},
     year = {2011},
     volume = {7},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SIGMA_2011_7_a41/}
}