Analyticity of the Boundary for Lipschitz Domains without the Pompeiu Property Stephen Williams Indiana University Mathematics Journal 1981 text pdf 10.1512/iumj.1981.30.30028 10.1512/iumj.1981.30.30028 en Indiana Univ. Math. J. 30 (1981) 357 - 369 state-of-the-art mathematics http://iumj.org/access/