@article{CMH_1993__68_2_140309,
     author = {J. Pipher and G. Verchota},
     title = {A maximum principle for biharmonic functions in {Lipschitz} and {C1} domains.},
     journal = {Commentarii mathematici Helvetici},
     pages = {385--414},
     publisher = {mathdoc},
     volume = {68},
     number = {2},
     year = {1993},
     zbl = {0794.31005},
     url = {http://geodesic.mathdoc.fr/item/CMH_1993__68_2_140309/}
}