@article{JRAM_1986__372_152877,
     author = {M., Wendland, W.L. Costabel},
     title = {Strong ellipticity of boundary integral operators.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {34--63},
     publisher = {mathdoc},
     volume = {372},
     year = {1986},
     zbl = {0628.35027},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1986__372_152877/}
}