@article{GDZPPN00220827X,
title = {Harmonic diffeomrophisms with roational symmetry.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {416},
year = {1991},
pages = {45-50},
zbl = {0726.58017},
url = {http://dml.mathdoc.fr/item/GDZPPN00220827X}
}
Hélein, Frédéric. Harmonic diffeomrophisms with roational symmetry.. Journal für die reine und angewandte Mathematik, Tome 416 (1991) pp. 45-50. http://gdmltest.u-ga.fr/item/GDZPPN00220827X/