A. General monographs on fuzzy logics

• Cintula, Petr, Petr Hájek, and Carles Noguera (eds.), 2011a, Handbook of Mathematical Fuzzy Logic, Volume 1, (Mathematical Logic and Foundations, Volume 37), London: College Publications.
• ––– (eds.), 2011b, Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications.
• Cintula, Petr, Christian Fermüller, and Carles Noguera (eds.), 2015, Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications.
• Gottwald, Siegfried, 2001, A Treatise On Many-Valued Logics, (Studies in Logic and Computation, Volume 9), Baldock: Research Studies Press Ltd.
• Hájek, Petr, 1998, Metamathematics of Fuzzy Logic (Trends in Logic, Volume 4), Dordrecht: Kluwer.

B. Fuzzy logics and fuzzy set theory

• Goguen, Joseph A., 1969, “The Logic of Inexact Concepts”, Synthese, 19(3–4): 325–373.
• Nguyen, Hung T., and Walker, Elbert A., 2005, A First Course in Fuzzy Logic (third edition), Chapman and Hall/CRC.
• Ross, Timothy J., 2016, Fuzzy Logic with Engineering Applications (fourth edition), Hoboken, NJ: Wiley.
• Zadeh, Lotfi A., 1965, “Fuzzy Sets”, Information and Control, 8(3): 338–353. doi:10.1016/S0019-9958(65)90241-X

C. Algebraic and real-valued semantics for fuzzy logics

• Aguzzoli, S., Bova, S., and Gerla, B., 2011, “Free algebras and functional representation for fuzzy logics”, in P. Cintula, P. Hájek, and C. Noguera, (editors), Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications, pages 713–719.
• Cintula, P., Esteva, F., Gispert, J., Godo, L., Montagna, F., and Noguera, C., 2009, “Distinguished Algebraic Semantics for T-Norm Based Fuzzy Logics: Methods and Algebraic Equivalencies”, Annals of Pure and Applied Logic, 160(1): 53–81.
• Horčík, Rostislav, 2011, “Algebraic Semantics: Semilinear FL-Algebras”, in P. Cintula, P. Hájek, and C. Noguera, (editors), Handbook of Mathematical Fuzzy Logic, Volume 1, (Mathematical Logic and Foundations, Volume 37), London: College Publications, pages 283–353.
• Jenei, Sándor and Franco Montagna, 2002, “A Proof of Standard Completeness for Esteva and Godo’s Logic MTL”, Studia Logica, 70(2): 183–192. doi:10.1023/A:1015122331293
• –––, 2003, “A Proof of Standard Completeness for Non-Commutative Monoidal T-norm Logic”, Neural Network World, 13(5): 481–489.
• Klement, Erich Peter, Radkos Mesiar, and Endre Pap, 2000, Triangular Norms, (Trends in Logic, Volume 8), Dordrecht: Kluwer.
• Ling, Cho-Hsin, 1965, “Representation of Associative Functions”, Publicationes Mathematicae Debrecen, 12: 189–212.
• Mostert, Paul S. and Allen L. Shields, 1957, “On the Structure of Semigroups on a Compact Manifold with Boundary”, The Annals of Mathematics, Second Series, 65(1): 117–143. doi:10.2307/1969668
• Vetterlein, T., 2015, “Algebraic Semantics: The Structure of Residuated Chains”, in P. Cintula, C. G. Fermüller, and C. Noguera, (editors), Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications, pages 929–967.

D. Game-theoretic semantics for fuzzy logics

• Cicalese, F., and Montagna, F., 2015, “Ulam-Rényi Game Based Semantics For Fuzzy Logics”, in P. Cintula, C.G. Fermüller, and C. Noguera, (editors), Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications, pages 1029–1062.
• Fermüller, Christian G., 2015, “Semantic Games for Fuzzy Logics”, in Cintula, Fermüller, and Noguera 2015: 969–1028.
• Fermüller, Christian G. and Christoph Roschger, 2014, “Randomized Game Semantics for Semi-Fuzzy Quantifiers”, Logic Journal of the Interest Group of Pure and Applied Logic, 22(3): 413–439. doi:10.1093/jigpal/jzt049
• Giles, Robin, 1974, “A Non-Classical Logic for Physics”, Studia Logica, 33(4): 397–415. doi:10.1007/BF02123379
• Mundici, D., 1992, “The Logic of Ulam's Game With Lies”, in C. Bicchieri, and M. Dalla Chiara, (editors), Knowledge, Belief, and Strategic Interaction (Castiglioncello, 1989), Cambridge: Cambridge University Press, 275–284.

E. Other semantics for fuzzy logics

• Běhounek, Libor, 2009, “Fuzzy Logics Interpreted as Logics of Resources”, in Michal Peliš (ed.), The Logica Yearbook 2008, London: College Publications, pp. 9–21.
• Hisdal, Ellen, 1988, “Are Grades of Membership Probabilities?” Fuzzy Sets and Systems, 25(3): 325–348. doi:10.1016/0165-0114(88)90018-8
• Lawry, J., 1998, “A Voting Mechanism for Fuzzy Logic”, International Journal of Approximate Reasoning, 19(3–4): 315–333. doi:10.1016/S0888-613X(98)10013-0
• Montagna, Franco, and Ono, Hiroakira, “Kripke Semantics, Undecidability and Standard Completeness for Esteva and Godo’s Logic MTL\(\forall\)”, Studia Logica, 71(2): 227–245.
• Paris, Jeff B., 1997, “A Semantics for Fuzzy Logic”, Soft Computing, 1(3): 143–147. doi:10.1007/s005000050015
• –––, 2000, “Semantics for Fuzzy Logic Supporting Truth Functionality”, in Vilém Novák and Irina Perfilieva (eds.), Discovering the World with Fuzzy Logic (Studies in Fuzziness and Soft Computing, Volume 57), Heidelberg: Springer, pp. 82–104.
• Ruspini, Enrique H., 1991, “On the Semantics of Fuzzy Logic”, International Journal of Approximate Reasoning, 5(1): 45–88. doi:10.1016/0888-613X(91)90006-8

F. Łukasiewicz logic

• Cignoli, R., D’Ottaviano, I.M., and Mundici, D., 1999, Algebraic Foundations of Many-Valued Reasoning, (Volume 7), Dordrecht: Kluwer.
• Hay, Louise Schmir, 1963, “Axiomatization of the Infinite-Valued Predicate Calculus”, Journal of Symbolic Logic, 28(1): 77–86. doi:10.2307/2271339
• Leştean, I., and DiNola, A., 2011, “Łukasiewicz Logic and MV-Algebras”, in P. Cintula, P. Hájek, and C. Noguera, (editors), Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications, pages 469–583.
• Łukasiewicz, Jan, 1920, “O Logice Trójwartościowej”, Ruch Filozoficzny, 5: 170–171. English translation, “On Three-Valued Logic”, in Storrs McCall, (editor), 1967, Polish Logic 1920–1939, Oxford: Clarendon Press, pages 16–18, and in Jan Łukasiewicz, 1970, Selected Works, L. Borkowski, (editor), Amsterdam: North-Holland, pages 87–88.
• Łukasiewicz, J. and A. Tarski, 1930, “Untersuchungen über den Aussagenkalkül”, Comptes Rendus Des Séances de La Société Des Sciences et Des Lettres de Varsovie, Cl. III, 23(iii): 30–50.
• McNaughton, Robert, 1951, “A Theorem About Infinite-Valued Sentential Logic”, Journal of Symbolic Logic, 16(1): 1–13. doi:10.2307/2268660
• Mundici, D., 2011, Advanced Łukasiewicz Calculus and MV-Algebras, (Trends in Logic, Volume 35), New York: Springer.

G. Gödel logics

• Baaz, Matthias, 1996, “Infinite-Valued Gödel Logic with 0–1-Projections and Relativisations”, in Petr Hájek (ed.), Gödel’96: Logical Foundations of Mathematics, Computer Science, and Physics (Lecture Notes in Logic, vol. 6), Brno: Springer, pages 23–33
• Baaz, Matthias, and Preining, Norbert, 2011, “Gödel-Dummett Logics”, in Cintula, Petr, Petr Hájek, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications, pages 585–625.
• Dummett, Michael, 1959, “A Propositional Calculus with Denumerable Matrix”, Journal of Symbolic Logic, 24(2): 97–106. doi:10.2307/2964753
• Gödel, Kurt, 1932, “Zum intuitionistischen Aussagenkalkül”, Anzeiger Akademie Der Wissenschaften Wien, 69: 65–66.
• Horn, Alfred, 1969, “Logic with Truth Values in a Linearly Ordered Heyting Algebra”, The Journal of Symbolic Logic, 34(3): 395–408.

H. Other fuzzy logics

• Busaniche, Manuela, and Montagna, Franco, 2011, “Hájek’s Logic BL and BL-Algebras”, in Cintula, Petr, Petr Hájek, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 1, (Mathematical Logic and Foundations, Volume 37), London: College Publications, pages 355–447.
• Esteva, Francesc, Joan Gispert, Lluís Godo, and Carles Noguera, 2007, “Adding Truth-Constants to Logics of Continuous T-Norms: Axiomatization and Completeness Results”, Fuzzy Sets and Systems, 158(6): 597–618. doi:10.1016/j.fss.2006.11.010
• Esteva, Francesc, and Lluís Godo, 2001, “Monoidal T-Norm Based Logic: Towards a Logic for Left-Continuous T-Norms”, Fuzzy Sets and Systems, 124(3): 271–288. doi:10.1016/S0165-0114(01)00098-7
• Esteva, Francesc, Lluís Godo, Petr Hájek, and Mirko Navara, 2000, “Residuated Fuzzy Logics with an Involutive Negation”, Archive for Mathematical Logic, 39(2): 103–124. doi:10.1007/s001530050006
• Esteva, Francesc, Godo, Lluís, and Marchioni, Enrico, 2011, “Fuzzy Logics with Enriched Language”, in Cintula, Petr, Petr Hájek, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications, pages 627–711.
• Esteva, Francesc, Lluís Godo, and Franco Montagna, 2001, “The \(L\Pi\) and \(L\Pi\frac12\) Logics: Two Complete Fuzzy Systems Joining Łukasiewicz and Product Logics”, Archive for Mathematical Logic, 40(1): 39–67. doi:10.1007/s001530050173
• –––, 2003, “Axiomatization of Any Residuated Fuzzy Logic Defined by a Continuous T-Norm”, in Taner Bilgiç, Bernard De Baets, and Okyay Kaynak (eds.), Fuzzy Sets and Systems: IFSA 2003 (Lecture Notes in Computer Science, vol. 2715), Berlin/Heidelberg: Springer, pp. 172–179. doi:10.1007/3-540-44967-1_20
• Hájek, Petr, 2001, “On Very True”, Fuzzy Sets and Systems, 124(3): 329–333.
• Haniková, Zuzana, 2014, “Varieties Generated by Standard BL-Algebras”, Order, 31(1): 15–33. doi:10.1007/s11083-013-9285-5
• Montagna, Franco, Noguera, Carles, and Horčík, Rostislav, 2006, “On Weakly Cancellative Fuzzy Logics”, Journal of Logic and Computation, 16(4): 423–450.

I. Fuzzy logics as substructural logics

• Cintula, Petr, Rostislav Horčík, and Carles Noguera, 2013, “Non-Associative Substructural Logics and their Semilinear Extensions: Axiomatization and Completeness Properties”, The Review of Symbolic Logic, 6(3): 394–423. doi:10.1017/S1755020313000099
• –––, 2014, “The Quest for the Basic Fuzzy Logic”, in Franco Montagna (ed.), Petr Hájek on Mathematical Fuzzy Logic (Outstanding Contributions to Logic, vol. 6), Cham: Springer, pp. 245–290. doi:10.1007/978-3-319-06233-4_12
• Esteva, Francesc, Godo, Lluís, and García-Cerdaña, Àngel, 2003, “On the Hierarchy of t-norm Based Residuated Fuzzy Logics”, in Fitting, Melvin, and Orłowska, Ewa, (editors), Beyond Two: Theory and Applications of Multiple-Valued Logic, (Studies in Fuzziness and Soft Computing, Volume 114), Heidelberg: Springer, pages 251–272.
• Galatos, Nikolaos, Jipsen, Peter, Kowalski, Tomasz, and Ono, Hiroakira, (editors), 2007, Residuated Lattices: An Algebraic Glimpse at Substructural Logics, (Studies in Logic and the Foundations of Mathematics, Volume 151), Amsterdam: Elsevier.
• Metcalfe, George and Franco Montagna, 2007, “Substructural Fuzzy Logics”, Journal of Symbolic Logic, 72(3): 834–864. doi:10.2178/jsl/1191333844

J. Fuzzy logics in abstract algebraic logic

• Běhounek, Libor, and Cintula, Petr, 2006, “Fuzzy Logics as the Logics of Chains”, Fuzzy Sets and Systems, 157(5): 604–610.
• Cintula, Petr, 2006, “Weakly impredicative (fuzzy) logics I: Basic properties”, Archive for Mathematical Logic, 45(6): 673–704.
• Cintula, Petr, and Noguera, Carles, 2011, “A General Framework for Mathematical Fuzzy Logic”, in Cintula, Petr, Petr Hájek, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 1, (Mathematical Logic and Foundations, Volume 37), London: College Publications, pages 103–207.
• Font, Josep Maria, 2016, Abstract Algebraic Logic: An Introductory Textbook, (Mathematical Logic and Foundations, Volume 60), London: College Publications.

K. First- and higher-fuzzy logics

• Běhounek, Libor, and Cintula, Petr, 2005, “Fuzzy Class Theory”, Fuzzy Sets and Systems, 154(1): 34–55.
• Běhounek, Libor, and Haniková, Zuzana, 2014, “Set Theory and Arithmetic in Fuzzy Logic”, in Montagna, Franco, (editor), Petr Hájek on Mathematical Fuzzy Logic, (Outstanding Contributions to Logic, Volume 6), Cham: Springer, pages 63–89.
• Dellunde, P., 2012, “Preserving Mappings in Fuzzy Predicate Logics”, Journal of Logic and Computation, 22(6): 1367–1389.
• Di Nola, A., and Gerla, G., 1986, “Fuzzy Models of First-Order Languages”, Zeitschrift für Mathematische Logik und Grundlagen der Mathematik, 32(19–24): 331–340.
• Hájek, P., and Cintula, P., 2006, “On Theories and Models in Fuzzy Predicate Logics”, Journal of Symbolic Logic, 71(3): 863–880.
• Hájek, P., and Haniková, Z., 2003, “A Development of Set Theory in Fuzzy Logic”, in Fitting, Melvin, and Orłowska, Ewa, (editors), Beyond Two: Theory and Applications of Multiple-Valued Logic, (Studies in Fuzziness and Soft Computing, Volume 114), Heidelberg: Springer, pages 273–285.
• Háajek, P., Paris, J., and Shepherdson, J.C., 2000, “The Liar Paradox and Fuzzy Logic”, Journal of Symbolic Logic, 65(1): 339–346.
• Novák, V., 2004, “On Fuzzy Type Theory”, Fuzzy Sets and Systems, 149(2): 235–273.
• Takeuti, G., and Titani, S., 1984, “Intuitionistic Fuzzy Logic and Intuitionistic Fuzzy Set Theory”, Journal of Symbolic Logic, 49(3): 851–866.
• Takeuti, G., and Titani, S., 1992, “Fuzzy Logic and Fuzzy Set Theory”, Archive for Mathematical Logic, 32(1): 1–32.

L. Complexity of fuzzy logics

• Baaz, M., Hájek, P., Montagna, F., and Veith, H., 2002, “Complexity of T-Tautologies”, Annals of Pure and Applied Logic, 113(1–3): 3–11.
• Hájek, P., Montagna, F., & Noguera, C., 2011, “Arithmetical Complexity of First-Order Fuzzy Logics”, in Cintula, Petr, Hájek, Petr, and Noguera, Carles, (editors), Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications, pages 853–908.
• Haniková, Zuzana, 2011, “Computational Complexity of Propositional Fuzzy Logics”, in Cintula, Petr, Hájek, Petr, and Noguera, Carles, (editors), Handbook of Mathematical Fuzzy Logic, Volume 2, (Mathematical Logic and Foundations, Volume 38), London: College Publications, pages 793–851.
• Montagna, Franco, 2001, “Three Complexity Problems in Quantified Fuzzy Logic”, Studia Logica, 68(1): 143–152. doi:10.1023/A:1011958407631
• Montagna, Franco and Carles Noguera, 2010, “Arithmetical Complexity of First-Order Predicate Fuzzy Logics Over Distinguished Semantics”, Journal of Logic and Computation, 20(2): 399–424. doi:10.1093/logcom/exp052
• Mundici, D., 1987, &ldauo;Satisfiability in Many-Valued Sentential Logic Is NP-Complete”, Theoretical Computer Science, 52(1–2): 145–153.
• Ragaz, Matthias Emil, 1981, Arithmetische Klassifikation von Formelmengen der unendlichwertigen Logik (PhD thesis). Swiss Federal Institute of Technology, Zürich. doi:10.3929/ethz-a-000226207
• Scarpellini, Bruno, 1962, “Die Nichtaxiomatisierbarkeit des unendlichwertigen Prädikatenkalküls von Łukasiewicz”, Journal of Symbolic Logic, 27(2): 159–170. doi:10.2307/2964111

M. Proof theory for fuzzy logics

• Avron, Arnon, 1991, “Hypersequents, Logical Consequence and Intermediate Logics for Concurrency”, Annals of Mathematics and Artificial Intelligence, 4(3–4): 225–248. doi:10.1007/BF01531058
• Ciabattoni, A., Galatos, N., and Terui, K., 2012, “Algebraic Proof Theory for Substructural Logics: Cut-Elimination and Completions”, Annals of Pure and Applied Logic, 163(3): 266–290.
• Fermüller, Christian G., and George Metcalfe, 2009, “Giles’s Game and Proof Theory for Łukasiewicz Logic”, Studia Logica, 92(1): 27–61. doi:10.1007/s11225-009-9185-2
• Metcalfe, George, 2011, “Proof Theory for Mathematical Fuzzy Logic”, in Cintula, Petr, Petr Hájek, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 1, (Mathematical Logic and Foundations, Volume 37), London: College Publications, pages 209–282.
• Metcalfe, George, Nicola Olivetti, and Dov M. Gabbay, 2008, Proof Theory for Fuzzy Logics (Applied Logic Series, vol. 36), Dordrecht: Springer Netherlands.

N. Structural completeness and unification in fuzzy logics

• Cintula, P., and Metcalfe, G., 2009, “Structural Completeness in Fuzzy Logics”, Notre Dame Journal of Formal Logic, 50(2): 153–183.
• Jeřábek, E., 2010, “Bases of Admissible Rules of Łukasiewicz Logic”, Journal of Logic and Computation, 20(6): 1149–1163.
• Marra, V., and Spada, L., 2013, “Duality, Projectivity, and Unification in řukasiewicz Logic and MV-Algebras”, Annals of Pure and Applied Logic, 164(3): 192–210.

O. Modal fuzzy logics

• Bou, F., Esteva, F., Godo, L., and Rodríguez, R.O., 2011, “On the Minimum Many-Valued Modal Logic Over a Finite Residuated Lattice”, Journal of Logic and Computation, 21(5): 739–790.
• Caicedo, X., and Rodríguez, R.O., 2010, “Standard Gödel Modal Logics”, Studia Logica, 94(2): 189–214.
• Hansoul, G., and Teheux, B., 2013, “Extending řukasiewicz Logics With a Modality: Algebraic Approach to Relational Semantics”, Studia Logica, 101(3): 505–545, doi: 10.1007/s11225-012-9396-9.

P. Description fuzzy logics

• Bobillo, F., Cerami, M., Esteva, F., García-Cerdaña, À., Peñaloza, R., and Straccia, U., 2015, “Fuzzy Description Logics”, in Cintula, P., Fermüller, C.G. , and Noguera, C., (editors), Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications, pages 1105–1181.
• García-Cerdaña, À., Armengol, E., and Esteva, F., 2010, “Fuzzy Description Logics and T-Norm Based Fuzzy Logics”, International Journal of Approximate Reasoning, 51(6): 632–655.
• Hájek, P., 2005, “Making Fuzzy Description Logic More General”, Fuzzy Sets and Systems, 154(1): 1–15.
• Straccia, U., 1998, “A Fuzzy Description Logic”, in Mostow, J., and Rich, C., (editors), Proceedings of the 15th National Conference on Artificial Intelligence (AAAI 1998), Menlo Park: AAAI Press, pages 594–599.

Q. Probability and fuzzy logics

• Fedel, M., Hosni, H., and Montagna, F., 2011, “A Logical Characterization of Coherence for Imprecise Probabilities”, International Journal of Approximate Reasoning, 52(8): 1147–1170, doi: 10.1016/j.ijar.2011.06.004.
• Flaminio, T., Godo, L., and Marchioni, E., 2011, “Reasoning About Uncertainty of Fuzzy Events: An Overview”, in Cintula, Petr, Fermuller, Christian G., Godo, Lluis, and Hájek, Petr, (editors), Understanding Vagueness: Logical, Philosophical, and Linguistic Perspectives, (Studies in Logic, Volume 36), London: College Publications, pages 367–400.
• Flaminio, T., and Kroupa, T., 2015, “States of MV-Algebras”, in Cintula, Petr, Christian Fermüller, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications, pages 1183–1236.
• Godo, L., Esteva, F., and Hájek, P., 2000, “Reasoning About Probability Using Fuzzy Logic”, Neural Network World, 10(5): 811–823, (Special Issue on SOFSEM 2000).

R. Other approaches to fuzzy logic

• Bělohlávek, R., and Vychodil, V., 2005, Fuzzy Equational Logic, (Studies in Fuzziness and Soft Computing, Volume 186), Berlin and Heidelberg: Springer.
• Gerla, G., 2001, Fuzzy Logic—Mathematical Tool for Approximate Reasoning, (Trends in Logic, Volume 11), New York: Kluwer and Plenum Press.
• Novák, V., 2015, “Fuzzy Logic With Evaluated Syntax”, in Cintula, Petr, Christian Fermüller, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications, pages 1063–1104.
• Novák, V., Perfilieva, I., and Močkoř, J., 2000, Mathematical Principles of Fuzzy Logic, Dordrecht: Kluwer.
• Pavelka, J., 1979, “On Fuzzy Logic I, II, and III”, Zeitschrift für Mathematische Logik und Grundlagen der Mathematik, 25: 45–52, 119–134, and 447–464.

S. Vagueness and fuzzy logics

• Běhounek, Libor, 2014, “In Which Sense Is Fuzzy Logic a Logic For Vagueness?”, in Lukasiewicz, Thomas, Peñaloza, Rafael, and Turhan, Anni-Yasmin, (editors), PRUV 2014: Logics for Reasoning About Preferences, Uncertainty, and Vagueness, (CEUR Workshop Proceedings, Volume 1205), Dresden: CEUR.
• Hájek, Petr, and Vilém Novák, 2003, “The Sorites Paradox and Fuzzy Logic”, International Journal of General Systems, 32(4): 373–383. doi:10.1080/0308107031000152522
• Smith, Nicholas J.J., 2005, “Vagueness as Closeness”, Australasian Journal of Philosophy, 83(2): 157–183. doi:10.1080/00048400500110826
• –––, 2008, Vagueness and Degrees of Truth, Oxford: Oxford University Press.
• –––, 2015, “Fuzzy Logics in Theories of Vagueness”, in Cintula, Petr, Christian Fermüller, and Carles Noguera (eds.), Handbook of Mathematical Fuzzy Logic, Volume 3, (Mathematical Logic and Foundations, Volume 58), London: College Publications, pages 1237–1281.