@article{MZ_1988__199_1_173968,
     author = {Alberto Baider and Richard Churchill},
     title = {Unique {Normal} {Forms} for {Planar} {Vector} {Fields.}},
     journal = {Mathematische Zeitschrift},
     pages = {303--310},
     publisher = {mathdoc},
     volume = {199},
     number = {1},
     year = {1988},
     zbl = {0691.58012},
     url = {http://geodesic.mathdoc.fr/item/MZ_1988__199_1_173968/}
}