A Note on Closed Degrees of Difficulty o
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Caterina Bianchini; Andrea Sorbi
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Article
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1996
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John Wiley and Sons
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English
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We consider some nonprincipal filters of the Medvedev lattice. We prove that the filter generated by the nonzero closed degrees of difficulty is not principal and we compare this filter, with respect to inclusion, with some other filters of the lattice. All the filters considered in this paper are d