On estimating $\exp(-iHt)$ when $H$ is perturbed

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Let us assume that we have an unbounded Hamiltonian $H$ and we perturb it a bit to be $H'=H+ \varepsilon A$. I am sure that estimating $||\exp(-iHt) - \exp(-iH't)||$ belongs to the subject of perturbation theory. Can you recommend me some resource (preferably textbooks) dealing with the topic?