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)
@misc(vanmodern,
 author       = {Johan van Benthem and Nick Bezhanishvili},
 title        = {Modern faces of filtration},
 note         = {ILLC Prepublication PP-2019-13},
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@phdthesis(carreiro2015fragments,
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 title        = {Fragments of fixpoint logics},
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)
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 title        = {Continuous fragment of the mu-calculus},
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@book(goldblatt1987logics,
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 title        = {On the Expressive Completeness of the Propositional $\mu$-Calculus w.r.t.\ Monadic Second-Order Logic},
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 volume       = {1119},
 pages        = {263--277},
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@inproceedings(kikot2020completeness,
 author       = {Stanislav Kikot and Ilya Shapirovsky and Evgeny Zolin},
 year         = {2020},
 title        = {Modal Logics with Transitive Closure: Completeness, Decidability, Filtration},
 editor       = {Nicola Olivetti and Rineke Verbrugge and Sara Negri and Gabriel Sandu},
 booktitle    = {13th Conference on Advances in Modal Logic, AiML 2020, Helsinki, Finland, August 24-28, 2020},
 publisher    = {College Publications},
 pages        = {369--388},
)
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 author       = {Dexter Kozen},
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 author       = {Dexter Kozen and Rohit Parikh},
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@book(lemmon1977introduction,
 author       = {John Lemmon and Dana Scott},
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 title        = {An introduction to modal logic},
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@misc(martivenemafocus,
 author       = {Johannes Marti and Yde Venema},
 year         = {2021},
 title        = {Focus-style proof systems and interpolation for the alternation-free $\mu$-calculus},
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