Positive Real Matrices Paul SlepianLouis Weinberg Indiana University Mathematics Journal 1960 text pdf 10.1512/iumj.1960.9.59004 10.1512/iumj.1960.9.59004 en Indiana Univ. Math. J. 9 (1960) 71 - 83 state-of-the-art mathematics http://iumj.org/access/