On the Orthogonal Equivalence of Sets of Real Symmetric Matrices A. Albert Indiana University Mathematics Journal 1958 text pdf 10.1512/iumj.1958.7.57018 10.1512/iumj.1958.7.57018 en Indiana Univ. Math. J. 7 (1958) 219 - 235 state-of-the-art mathematics http://iumj.org/access/