Multiple positive and nodal solutions for semilinear elliptic problems with critical exponents Daomin CaoEzzat Noussair Indiana University Mathematics Journal 1995 text pdf 10.1512/iumj.1995.44.2027 10.1512/iumj.1995.44.2027 en Indiana Univ. Math. J. 44 (1995) 1249 - 1272 state-of-the-art mathematics http://iumj.org/access/