@article{10_2307_121055,
     author = {Edward R. Goetze and Ralf J. Spatzier},
     title = {Smooth classification of {Cartan} actions of higher rank semisimple {Lie} groups and their lattices},
     journal = {Annals of mathematics},
     year = {1999},
     volume = {150},
     number = {3},
     doi = {10.2307/121055},
     zbl = {0940.22011},
     url = {http://geodesic.mathdoc.fr/articles/10.2307/121055/}
}