The Dirichlet Problem for the Biharmonic Equation in C^1 Domains Gregory Verchota Indiana University Mathematics Journal 1987 text pdf 10.1512/iumj.1987.36.36048 10.1512/iumj.1987.36.36048 en Indiana Univ. Math. J. 36 (1987) 867 - 895 state-of-the-art mathematics http://iumj.org/access/