**CONTENTS**

*George Avalos, Irena Lasiecka *Exponential stability of a thermoelastic system without mechanical dissipation

*Viorel Barbu, Angelo Favini *Periodic problems for degenerate differential equations

*Viorel Barbu, Mimmo Iannelli *The semigroup approach to non-linear age-structured equations

*Bernard Beauzamy *Extremal products in Bombieri's norm

*Shangquan Bu, Sylvie Guerre-Delabriere *Imaginary powers and Interpolation spaces of unbounded operators

*Giuseppe Da Prato *Perturbation of Ornstein-Uhlenbeck semigroups

*H. O. Fattorini *Nonlinear infinite dimensional optimal control problems with state constraints and unbounded control sets

*Marco Fuhrman *On the sum of generators of analytic semigroups

*Ugo Gianazza, Vincenzo Vespri *Analytic semigroups generated by square Hörmander Operators

*Hans-Christoph Grunau, Wolf Von Wahl *Regularity considerations for semilinear parabolic systems

*Matthias Hieber *Gaussian estimates and invariance of the

*L*-Spectrum for elliptic operators of higher order

^{p}*Alessandra Lunardi, Vincenzo Vespri *Generation of strongly continous semigroups by elliptic operators with unbounded coefficients in

*L*(R

^{p}*)*

^{n}*J. M. A. M. Van Neerven *Elementary operator-theoretic proof of Wienner's Tauberian Theorem

*Jan Prüss *Poisson estimates and maximal regularity for evolutionary integral equations in

*L*-spaces

_{p}*Eugenio Sinestrari *Favard classes and hyperbolic equations

*Pavel E. Sobolevskii *Well-Posedness of difference elliptic equation

*Guido Sweers *Hopf's Lemma and two dimensional domains with corners

*Horst R. Thieme *On commutative sums of generators

*Roberto Triggiani *Carleman estimates and exact boundary controllabilty for a system of coupled non-conservative Schödinger Equations

** Editorial policy**
The journal *Rendiconti dell’Istituto di Matematica dell’università di Trieste * publishes original articles in all areas of mathematics. Special regard is given to research papers, but attractive expository papers may also be considered for publication.
The journal usually appears in one issue per year. Additional issues may however be published. In particular, the Managing Editors may consider the publication of supplementary volumes related to some special events, like conferences, workshops, and advanced schools.
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