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Creators/Authors contains: "CSIMA, BARBARA F."

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  1. ; ; ; (, The Bulletin of Symbolic Logic)
    Abstract When classes of structures are not first-order definable, we might still try to find a nice description. There are two common ways for doing this. One is to expand the language, leading to notions of pseudo-elementary classes, and the other is to allow infinite conjuncts and disjuncts. In this paper we examine the intersection. Namely, we address the question: Which classes of structures are both pseudo-elementary and $${\mathcal {L}}_{\omega _1, \omega }$$ -elementary? We find that these are exactly the classes that can be defined by an infinitary formula that has no infinitary disjunctions. 
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  2. ; ; ; ; ; ; ; ; ; (, Computability)
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