@article{JOLT_2008_18_3_a1,
     author = {M. Jotz and K.-H. Neeb},
     title = {Closedness of the {Tangent} {Spaces} to the {Orbits} of {Proper} {Actions}},
     journal = {Journal of Lie Theory},
     pages = {517--521},
     year = {2008},
     volume = {18},
     number = {3},
     doi = {10.5802/jolt.508},
     zbl = {1157.22011},
     url = {https://jolt.centre-mersenne.org/articles/10.5802/jolt.508/}
}