Smoothness of Bessel Potentials and Lipschitz Functions C. Neugebauer Indiana University Mathematics Journal 1977 text pdf 10.1512/iumj.1977.26.26046 10.1512/iumj.1977.26.26046 en Indiana Univ. Math. J. 26 (1977) 585 - 591 state-of-the-art mathematics http://iumj.org/access/