Multiple solutions and regularity of H-systems Libin MouPaul Yang Indiana University Mathematics Journal 1996 text pdf 10.1512/iumj.1996.45.949 10.1512/iumj.1996.45.949 en Indiana Univ. Math. J. 45 (1996) 1193 - 1224 state-of-the-art mathematics http://iumj.org/access/