An Invariant Fomulation of the New Maximum-Minimum Theory of Eigenvalues Alexander Weinstein Indiana University Mathematics Journal 1967 text pdf 10.1512/iumj.1967.16.16015 10.1512/iumj.1967.16.16015 en Indiana Univ. Math. J. 16 (1967) 213 - 218 state-of-the-art mathematics http://iumj.org/access/