1. Stål O. Aanderaa, Egon Börger & Harry R. Lewis (1982). Conservative Reduction Classes of Krom Formulas. Journal of Symbolic Logic 47 (1):110-130.
    A Krom formula of pure quantification theory is a formula in conjunctive normal form such that each conjunct is a disjunction of at most two atomic formulas or negations of atomic formulas. Every class of Krom formulas that is determined by the form of their quantifier prefixes and which is known to have an unsolvable decision problem for satisfiability is here shown to be a conservative reduction class. Therefore both the general satisfiability problem, and the problem of satisfiability in finite (...)
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  2. Stal O. Aanderaa & Harry R. Lewis (1974). Linear Sampling and the |Forall |Exists |Forall Case of the Decision Problem. Journal of Symbolic Logic 39 (3):519 - 548.
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  3. Stål O. Aanderaa & Harry R. Lewis (1973). Prefix Classes of Krom Formulas. Journal of Symbolic Logic 38 (4):628-642.
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