@article{10_1090_S0894_0347_1991_1086967_2,
     author = {Lu, Jiang-Hua and Ratiu, Tudor},
     title = {On the nonlinear convexity theorem of {Kostant}},
     journal = {Journal of the American Mathematical Society},
     pages = {349--363},
     publisher = {mathdoc},
     volume = {04},
     number = {2},
     year = {1991},
     doi = {10.1090/S0894-0347-1991-1086967-2},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-1991-1086967-2/}
}