@article{GDZPPN002196603,
title = {Regularity results for some classes of higher order non linear elliptic systems.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {310},
year = {1979},
pages = {145-169},
zbl = {0409.35015},
url = {http://dml.mathdoc.fr/item/GDZPPN002196603}
}
Giaquinta, M.; Modica, G. Regularity results for some classes of higher order non linear elliptic systems.. Journal für die reine und angewandte Mathematik, Tome 310 (1979) pp. 145-169. http://gdmltest.u-ga.fr/item/GDZPPN002196603/