The L^2 Behavior of Eigenfunction Expansions Harold Benzinger Indiana University Mathematics Journal 1976 text pdf 10.1512/iumj.1976.25.25053 10.1512/iumj.1976.25.25053 en Indiana Univ. Math. J. 25 (1976) 691 - 702 state-of-the-art mathematics http://iumj.org/access/