@article{GFA_1994__4_6_58162,
     author = {M. Ratner},
     title = {Invariant {Measures} and {Orbit} {Closures} for {Unipotent} {Action} on {Homogeneous} {Spaces} {(Survey).}},
     journal = {Geometric and functional analysis},
     pages = {236--258},
     publisher = {mathdoc},
     volume = {4},
     number = {6},
     year = {1994},
     zbl = {0801.22008},
     url = {http://geodesic.mathdoc.fr/item/GFA_1994__4_6_58162/}
}