@article{JRAM_1991__414_153298,
     author = {Fr\'ed\'eric H\'elein},
     title = {Harmonic diffeomrophisms with roational symmetry.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {45--50},
     year = {1991},
     volume = {414},
     zbl = {0726.58017},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1991__414_153298/}
}