This is the abstract of the paper
  "Evolutionary Coprocesses and Perturbations
   of Kato-stable Families of Operators "
by Stefano Bertoni.

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Abstract: In this paper we introduce and study a new object, a
{\em co-process} $ U^\oplus(t,s) $, associated to an evolutionary process
$ U(t,s) $, $ 0\leq s\leq t\leq T $, generated by a family
$ \{A(t)\}_{0\leq t\leq T} $ of operators.
Moreover, to prove a theorem of existence for the co-process,
we obtain a theorem of Kato-stability for a family of operators with
respect to perturbations given in a constant domain.

Key words: evolutionary process,
           non-autonomous linear abstract differential equation,
           co-process, family of generators of $ C_0 $-semigroups,
           Kato-stability, perturbation.

AMS Subject Classification: 34G10, 47D03, 47A55.