@article{IM_1978__48_142583,
     author = {Hing-Sun Luk},
     title = {Normalization of {Differential} {Equations} {Defining} a {CR} {Structure.}},
     journal = {Inventiones mathematicae},
     pages = {33--60},
     publisher = {mathdoc},
     volume = {48},
     year = {1978},
     zbl = {0389.32006},
     url = {http://geodesic.mathdoc.fr/item/IM_1978__48_142583/}
}