Addendum to Asymptotic Distribution of the Eigenvalues of the Lower Part of the Schroedinger Operator Spectrum' F. BrownellC. Clark Indiana University Mathematics Journal 1961 text pdf 10.1512/iumj.1961.10.10033 10.1512/iumj.1961.10.10033 en Indiana Univ. Math. J. 10 (1961) 525 - 527 state-of-the-art mathematics http://iumj.org/access/