Nabutovsky, Alexander Max Planck Institute for Mathematics, Max Planck Society;
Rotman, Regina Max Planck Institute for Mathematics, Max Planck Society;
Nabutovsky, A., & Rotman, R. (2009). Length of geodesics on a two-dimensional sphere. American Journal of Mathematics, 131(2), 545-569. doi:10.1353/ajm.0.0042.