Distribution of the eigenvalues of the Sturm–Liouville operator equation

This work contains an analysis of the dependence of the lower terms of the asymptotics of the distribution of the eigenvalues of the equation $-y''+Ay=\lambda y$ upon the spectrum of the positive selfadjoint operator $A$ and the form of the boundary conditions. As a corollary the second term is found for the spectral asymptotics of classical boundary value problems for the Laplace equation in three-dimensional cylindrical domains.
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