@article{IM_1981__64_142820,
     author = {Alan Weinstein and Christpher B. Croke},
     title = {Closed {Curves} on {Convex} {Hypersurfaces} and {Periods} of {Nonlinear} {Oscillations.}},
     journal = {Inventiones mathematicae},
     pages = {199--202},
     publisher = {mathdoc},
     volume = {64},
     year = {1981},
     zbl = {0471.70020},
     url = {http://geodesic.mathdoc.fr/item/IM_1981__64_142820/}
}