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  1. Saverio Cittadini & Carlo Toffalori (2006). On Pairs of Free Modules Over a Dedekind Domain. Archive for Mathematical Logic 45 (1):75-95.
    The study of pairs of modules (over a Dedekind domain) arises from two different perspectives, as a starting step in the analysis of tuples of submodules of a given module, or also as a particular case in the analysis of Abelian structures made by two modules and a morphism between them. We discuss how these two perspectives converge to pairs of modules, and we follow the latter one to obtain an alternative approach to the classification of pairs of torsionfree objects. (...)
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  2. Saverio Cittadini & Carlo Toffalori (2002). Comparing First Order Theories of Modules Over Group Rings. Mathematical Logic Quarterly 48 (1):147-156.
    We consider R-torsionfree modules over group rings RG, where R is a Dedekind domain and G is a finite group. In the first part of the paper [4] we compared the theory T of all R-torsionfree RG-modules and the theory T0 of RG-lattices , and we realized that they are almost always different. Now we compare their behaviour with respect to decidability, when RG-lattices are of finite, or wild representation type.
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  3. Wilfried Sieg & Saverio Cittadini, Normal Natural Deduction Proof (In Non-Classical Logics).
    Wilfred Sieg and Saverio Cittadini. Normal Natural Deduction Proof (In Non-Classical Logics.
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  4. Fabio Bellissima & Saverio Cittadini (1999). Finite Trees in Tense Logic. Studia Logica 62 (2):121-140.
    In this paper we show the adequacy of tense logic with unary operators for dealing with finite trees. We prove that models on finite trees can be characterized by tense formulas, and describe an effective method to find an axiomatization of the theory of a given finite tree in tense logic. The strength of the characterization is shown by proving that adding the binary operators "Until" and "Since" to the language does not result in a better description than that given (...)
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  5. Fabio Bellissima & Saverio Cittadini (1999). Minimal P-Morphic Images, Axiomatizations and Coverings in the Modal Logic K. Studia Logica 62 (3):371-398.
    We define the concepts of minimal p-morphic image and basic p-morphism for transitive Kripke frames. These concepts are used to determine effectively the least number of variables necessary to axiomatize a tabular extension of K4, and to describe the covers and co-covers of such a logic in the lattice of the extensions of K4.
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  6. Fabio Bellissima & Saverio Cittadini (1998). Duality and Completeness for US-Logics. Notre Dame Journal of Formal Logic 39 (2):231-242.
    The semantics of e-models for tense logics with binary operators for `until' and `since' (US-logics) was introduced by Bellissima and Bucalo in 1995. In this paper we show the adequacy of these semantics by proving a general Henkin-style completeness theorem. Moreover, we show that for these semantics there holds a Stone-like duality theorem with the algebraic structures that naturally arise from US-logics.
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  7. Fabio Bellissima & Saverio Cittadini (1997). Minimal Axiomatization in Modal Logic. Mathematical Logic Quarterly 43 (1):92-102.
    We consider the problem of finding, in the ambit of modal logic, a minimal characterization for finite Kripke frames, i.e., a formula which, given a frame, axiomatizes its theory employing the lowest possible number of variables and implies the other axiomatizations. We show that every finite transitive frame admits a minimal characterization over K4, and that this result can not be extended to K.
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