2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/63718If $A(t)$ is a $C^{1,\al}$-curve of unbounded self-adjoint operators with compact resolvents and common domain of definition, then the eigenvalues can be parameterized $C^1$ in $t$. If $A$ is $C^\infty$ then the eigenvalues can be parameterized twice differentiable.amstex 9 pages. Some misprints correctedFunctional AnalysisAnalysis of PDEsSpectral Theory47A55; 47A75text