Edit Profile (opens in new tab) Gabbay, Murdoch James Co-Author Distance Author ID: gabbay.murdoch-james Published as: Gabbay, Murdoch J.; Gabbay, Murdoch; Gabbay, Murdoch James more...less Documents Indexed: 57 Publications since 2000, including 2 Additional arXiv Preprints 1 Further Contribution Co-Authors: 23 Co-Authors with 40 Joint Publications 524 Co-Co-Authors all top 5 Co-Authors 18 single-authored 7 Mathijssen, Aad 6 Pitts, Andrew M. 5 Gabbay, Michael J. 4 Fernández, Maribel 4 Mulligan, Dominic P. 3 Dowek, Gilles 2 Ghica, Dan R. 2 Lengrand, Stéphane Jean Eric 2 Petrisan, Daniela Luan 2 Reniers, Michel Adriaan 2 Urban, Christian 1 Aceto, Luca 1 Ayala-Rincón, Mauricio 1 Ciancia, Vincenzo 1 Cimini, Matteo 1 Fairweather, Elliot 1 Hofmann, Martin 1 Kropholler, Peter H. 1 Litak, Tadeusz 1 Mousavi, Mohamamdreza 1 Nanevski, Aleksandar 1 Rocha-Oliveira, Ana Cristina 1 Shinwell, Mark R. 1 Wirth, Claus-Peter all top 5 Serials 6 Journal of Logic and Computation 5 Information and Computation 3 Theoretical Computer Science 3 Mathematical Structures in Computer Science 3 Journal of Applied Logic 2 Formal Aspects of Computing 2 Logic Journal of the IGPL 1 The Journal of Symbolic Logic 1 Annals of Pure and Applied Logic 1 The Bulletin of Symbolic Logic 1 Journal of the ACM 1 Bulletin of the European Association for Theoretical Computer Science EATCS 1 ACM Transactions on Computational Logic 1 Logical Methods in Computer Science all top 5 Fields 41 Mathematical logic and foundations (03-XX) 39 Computer science (68-XX) 3 Order, lattices, ordered algebraic structures (06-XX) 3 Category theory; homological algebra (18-XX) 2 General algebraic systems (08-XX) 1 History and biography (01-XX) 1 Game theory, economics, finance, and other social and behavioral sciences (91-XX) 1 Information and communication theory, circuits (94-XX) Publications by Year all cited Publications top 5 cited Publications Citations contained in zbMATH Open 48 Publications have been cited 1,104 times in 491 Documents Cited by ▼ Year ▼ Stone duality for nominal Boolean algebras with {И}. Zbl 1241.68050 Gabbay, Murdoch J.; Litak, Tadeusz; Petrişan, Daniela 457 2011 A new approach to abstract syntax with variable binding. Zbl 1001.68083 Gabbay, Murdoch J.; Pitts, Andrew M. 162 2002 Nominal unification. Zbl 1078.68140 Urban, Christian; Pitts, Andrew M.; Gabbay, Murdoch J. 68 2004 FreshML: programming with binders made simple. Zbl 1315.68058 Shinwell, Mark R.; Pitts, Andrew M.; Gabbay, Murdoch J. 47 2003 Nominal rewriting. Zbl 1118.68075 Fernández, Maribel; Gabbay, Murdoch J. 43 2007 A metalanguage for programming with bound names modulo renaming. Zbl 0963.68502 Pitts, Andrew M.; Gabbay, Murdoch J. 32 2000 Nominal (universal) algebra: equational logic with names and binding. Zbl 1191.08003 Gabbay, Murdoch J.; Mathijssen, Aad 29 2009 Foundations of nominal techniques: logic and semantics of variables in abstract syntax. Zbl 1253.03059 Gabbay, Murdoch J. 16 2011 Capture-avoiding substitution as a nominal algebra. Zbl 1152.68025 Gabbay, Murdoch J.; Mathijssen, Aad 16 2008 Nominal unification. Zbl 1116.03322 Urban, Christian; Pitts, Andrew; Gabbay, Murdoch 16 2003 One-and-a-halfth-order logic. Zbl 1158.03006 Gabbay, Murdoch J.; Mathijssen, Aad 14 2008 Freshness and name-restriction in sets of traces with names. Zbl 1241.68049 Gabbay, Murdoch J.; Ciancia, Vincenzo 14 2011 Nominal renaming sets. Zbl 1182.03065 Gabbay, Murdoch J.; Hofmann, Martin 13 2008 Capture-avoiding substitution as a nominal algebra. Zbl 1152.68454 Gabbay, Murdoch J.; Mathijssen, Aad 13 2006 A formal calculus for informal equality with binding. Zbl 1213.03038 Gabbay, Murdoch J.; Mathijssen, Aad 13 2007 Permissive nominal terms and their unification: an infinite, co-infinite approach to nominal techniques. Zbl 1215.03048 Dowek, Gilles; Gabbay, Murdoch J.; Mulligan, Dominic P. 12 2010 A general mathematics of names. Zbl 1123.03047 Gabbay, Murdoch J. 11 2007 Nominal algebra and the HSP theorem. Zbl 1163.03017 Gabbay, Murdoch J. 10 2009 The \(\pi\)-calculus in FM. Zbl 1063.68073 Gabbay, Murdoch J. 9 2003 A nominal axiomatization of the lambda calculus. Zbl 1198.03023 Gabbay, Murdoch J.; Mathijssen, Aad 8 2010 SOS for higher order processes. Zbl 1134.68450 Mousavi, Mohammad Reza; Gabbay, Murdoch J.; Reniers, Michel A. 8 2005 One-and-a-halfth order terms: Curry-Howard and incomplete derivations. Zbl 1156.03013 Gabbay, Murdoch J.; Mulligan, Dominic P. 7 2008 Checking overlaps of nominal rewriting rules. Zbl 1401.68131 Ayala-Rincón, Mauricio; Fernández, Maribel; Gabbay, Murdoch James; Rocha-Oliveira, Ana Cristina 7 2016 A study of substitution, using nominal techniques and Fraenkel-Mostowksi sets. Zbl 1159.03019 Gabbay, Murdoch J. 7 2009 Fresh logic: Proof-theory and semantics for FM and nominal techniques. Zbl 1124.03010 Gabbay, Murdoch J. 7 2007 Nominal SOS. Zbl 1342.68193 Cimini, Matteo; Mousavi, Mohamamdreza; Reniers, Michel A.; Gabbay, Murdoch J. 6 2012 Leaving the nest: nominal techniques for variables with interleaving scopes. Zbl 1373.68179 Gabbay, Murdoch J.; Ghica, Dan R.; Petrisan, Daniela 5 2015 Permissive-nominal logic: first-order logic over nominal terms and sets. Zbl 1352.03042 Dowek, Gilles; Gabbay, Murdoch J. 5 2012 Meta-variables as infinite lists in nominal terms unification and rewriting. Zbl 1278.68119 Gabbay, Murdoch J. 5 2012 Curry-style types for nominal terms. Zbl 1178.68150 Fernández, Maribel; Gabbay, Murdoch J. 5 2007 Two-level nominal sets and semantic nominal terms: an extension of nominal set theory for handling meta-variables. Zbl 1228.68022 Gabbay, Murdoch J. 4 2011 The lambda-context calculus (extended version). Zbl 1192.68137 Gabbay, Murdoch J.; Lengrand, Stéphane 4 2009 Hierarchical nominal terms and their theory of rewriting. Zbl 1278.68120 Gabbay, Murdoch J. 3 2007 The \(\lambda\)-context calculus. Zbl 1278.03036 Gabbay, Murdoch J.; Lengrand, Stéphane 3 2008 Two-level lambda-calculus. Zbl 1347.68051 Gabbay, Murdoch J. 3 2009 Finite and infinite support in nominal algebra and logic: nominal completeness theorems for free. Zbl 1251.03035 Gabbay, Murdoch J. 3 2012 Game semantics in the nominal model. Zbl 1342.68195 Gabbay, Murdoch; Ghica, Dan 3 2012 A simple class of Kripke-style models in which logic and computation have equal standing. Zbl 1253.03058 Gabbay, Michael; Gabbay, Murdoch J. 3 2010 Semantics out of context: nominal absolute denotations for first-order logic and computation. Zbl 1426.68158 Gabbay, Murdoch J. 2 2016 Representation and duality of the untyped \(\lambda\)-calculus in nominal lattice and topological semantics, with a proof of topological completeness. Zbl 1422.03023 Gabbay, Murdoch J.; Gabbay, Michael 2 2017 The lambda-calculus is nominal algebraic. Zbl 1226.03028 Gabbay, Murdoch J.; Mathijssen, Aad 2 2008 Imaginary groups: lazy monoids and reversible computation. Zbl 1286.68132 Gabbay, Murdoch J.; Kropholler, Peter H. 1 2013 Equivariant ZFA and the foundations of nominal techniques. Zbl 1515.03203 Gabbay, Murdoch 1 2020 PNL to HOL: from the logic of nominal sets to the logic of higher-order functions. Zbl 1309.03013 Dowek, Gilles; Gabbay, Murdoch J. 1 2012 Denotation of contextual modal type theory (CMTT): syntax and meta-programming. Zbl 1280.03037 Gabbay, Murdoch J.; Nanevski, Aleksandar 1 2013 Some formal considerations on Gabbay’s restart rule in natural deduction and goal-directed reasoning. Zbl 1279.03078 Gabbay, Michael; Gabbay, Murdoch 1 2005 \(a\)-logic. Zbl 1284.03196 Gabbay, Murdoch J.; Gabbay, Michael J. 1 2005 Principal types for nominal theories. Zbl 1241.68048 Fairweather, Elliot; Fernández, Maribel; Gabbay, Murdoch J. 1 2011 Equivariant ZFA and the foundations of nominal techniques. Zbl 1515.03203 Gabbay, Murdoch 1 2020 Representation and duality of the untyped \(\lambda\)-calculus in nominal lattice and topological semantics, with a proof of topological completeness. Zbl 1422.03023 Gabbay, Murdoch J.; Gabbay, Michael 2 2017 Checking overlaps of nominal rewriting rules. Zbl 1401.68131 Ayala-Rincón, Mauricio; Fernández, Maribel; Gabbay, Murdoch James; Rocha-Oliveira, Ana Cristina 7 2016 Semantics out of context: nominal absolute denotations for first-order logic and computation. Zbl 1426.68158 Gabbay, Murdoch J. 2 2016 Leaving the nest: nominal techniques for variables with interleaving scopes. Zbl 1373.68179 Gabbay, Murdoch J.; Ghica, Dan R.; Petrisan, Daniela 5 2015 Imaginary groups: lazy monoids and reversible computation. Zbl 1286.68132 Gabbay, Murdoch J.; Kropholler, Peter H. 1 2013 Denotation of contextual modal type theory (CMTT): syntax and meta-programming. Zbl 1280.03037 Gabbay, Murdoch J.; Nanevski, Aleksandar 1 2013 Nominal SOS. Zbl 1342.68193 Cimini, Matteo; Mousavi, Mohamamdreza; Reniers, Michel A.; Gabbay, Murdoch J. 6 2012 Permissive-nominal logic: first-order logic over nominal terms and sets. Zbl 1352.03042 Dowek, Gilles; Gabbay, Murdoch J. 5 2012 Meta-variables as infinite lists in nominal terms unification and rewriting. Zbl 1278.68119 Gabbay, Murdoch J. 5 2012 Finite and infinite support in nominal algebra and logic: nominal completeness theorems for free. Zbl 1251.03035 Gabbay, Murdoch J. 3 2012 Game semantics in the nominal model. Zbl 1342.68195 Gabbay, Murdoch; Ghica, Dan 3 2012 PNL to HOL: from the logic of nominal sets to the logic of higher-order functions. Zbl 1309.03013 Dowek, Gilles; Gabbay, Murdoch J. 1 2012 Stone duality for nominal Boolean algebras with {И}. Zbl 1241.68050 Gabbay, Murdoch J.; Litak, Tadeusz; Petrişan, Daniela 457 2011 Foundations of nominal techniques: logic and semantics of variables in abstract syntax. Zbl 1253.03059 Gabbay, Murdoch J. 16 2011 Freshness and name-restriction in sets of traces with names. Zbl 1241.68049 Gabbay, Murdoch J.; Ciancia, Vincenzo 14 2011 Two-level nominal sets and semantic nominal terms: an extension of nominal set theory for handling meta-variables. Zbl 1228.68022 Gabbay, Murdoch J. 4 2011 Principal types for nominal theories. Zbl 1241.68048 Fairweather, Elliot; Fernández, Maribel; Gabbay, Murdoch J. 1 2011 Permissive nominal terms and their unification: an infinite, co-infinite approach to nominal techniques. Zbl 1215.03048 Dowek, Gilles; Gabbay, Murdoch J.; Mulligan, Dominic P. 12 2010 A nominal axiomatization of the lambda calculus. Zbl 1198.03023 Gabbay, Murdoch J.; Mathijssen, Aad 8 2010 A simple class of Kripke-style models in which logic and computation have equal standing. Zbl 1253.03058 Gabbay, Michael; Gabbay, Murdoch J. 3 2010 Nominal (universal) algebra: equational logic with names and binding. Zbl 1191.08003 Gabbay, Murdoch J.; Mathijssen, Aad 29 2009 Nominal algebra and the HSP theorem. Zbl 1163.03017 Gabbay, Murdoch J. 10 2009 A study of substitution, using nominal techniques and Fraenkel-Mostowksi sets. Zbl 1159.03019 Gabbay, Murdoch J. 7 2009 The lambda-context calculus (extended version). Zbl 1192.68137 Gabbay, Murdoch J.; Lengrand, Stéphane 4 2009 Two-level lambda-calculus. Zbl 1347.68051 Gabbay, Murdoch J. 3 2009 Capture-avoiding substitution as a nominal algebra. Zbl 1152.68025 Gabbay, Murdoch J.; Mathijssen, Aad 16 2008 One-and-a-halfth-order logic. Zbl 1158.03006 Gabbay, Murdoch J.; Mathijssen, Aad 14 2008 Nominal renaming sets. Zbl 1182.03065 Gabbay, Murdoch J.; Hofmann, Martin 13 2008 One-and-a-halfth order terms: Curry-Howard and incomplete derivations. Zbl 1156.03013 Gabbay, Murdoch J.; Mulligan, Dominic P. 7 2008 The \(\lambda\)-context calculus. Zbl 1278.03036 Gabbay, Murdoch J.; Lengrand, Stéphane 3 2008 The lambda-calculus is nominal algebraic. Zbl 1226.03028 Gabbay, Murdoch J.; Mathijssen, Aad 2 2008 Nominal rewriting. Zbl 1118.68075 Fernández, Maribel; Gabbay, Murdoch J. 43 2007 A formal calculus for informal equality with binding. Zbl 1213.03038 Gabbay, Murdoch J.; Mathijssen, Aad 13 2007 A general mathematics of names. Zbl 1123.03047 Gabbay, Murdoch J. 11 2007 Fresh logic: Proof-theory and semantics for FM and nominal techniques. Zbl 1124.03010 Gabbay, Murdoch J. 7 2007 Curry-style types for nominal terms. Zbl 1178.68150 Fernández, Maribel; Gabbay, Murdoch J. 5 2007 Hierarchical nominal terms and their theory of rewriting. Zbl 1278.68120 Gabbay, Murdoch J. 3 2007 Capture-avoiding substitution as a nominal algebra. Zbl 1152.68454 Gabbay, Murdoch J.; Mathijssen, Aad 13 2006 SOS for higher order processes. Zbl 1134.68450 Mousavi, Mohammad Reza; Gabbay, Murdoch J.; Reniers, Michel A. 8 2005 Some formal considerations on Gabbay’s restart rule in natural deduction and goal-directed reasoning. Zbl 1279.03078 Gabbay, Michael; Gabbay, Murdoch 1 2005 \(a\)-logic. Zbl 1284.03196 Gabbay, Murdoch J.; Gabbay, Michael J. 1 2005 Nominal unification. Zbl 1078.68140 Urban, Christian; Pitts, Andrew M.; Gabbay, Murdoch J. 68 2004 FreshML: programming with binders made simple. Zbl 1315.68058 Shinwell, Mark R.; Pitts, Andrew M.; Gabbay, Murdoch J. 47 2003 Nominal unification. Zbl 1116.03322 Urban, Christian; Pitts, Andrew; Gabbay, Murdoch 16 2003 The \(\pi\)-calculus in FM. Zbl 1063.68073 Gabbay, Murdoch J. 9 2003 A new approach to abstract syntax with variable binding. Zbl 1001.68083 Gabbay, Murdoch J.; Pitts, Andrew M. 162 2002 A metalanguage for programming with bound names modulo renaming. Zbl 0963.68502 Pitts, Andrew M.; Gabbay, Murdoch J. 32 2000 all cited Publications top 5 cited Publications all top 5 Cited by 545 Authors 23 Fernández, Maribel 23 Gabbay, Murdoch James 15 Ayala-Rincón, Mauricio 13 Pitts, Andrew M. 12 Tzevelekos, Nikos 10 Sobrinho, Daniele Nantes 8 Cheney, James 8 Murawski, Andrzej S. 7 Kurz, Alexander 7 Milius, Stefan 6 Ciancia, Vincenzo 6 Klin, Bartek 6 Parrow, Joachim 6 Urbat, Henning 5 Calvès, Christophe 5 Ferrari, Gian Luigi 5 Kutsia, Temur 5 Montanari, Ugo G. 5 Rocha-Oliveira, Ana Cristina 5 Schmidt-Schauß, Manfred 4 Åman Pohjola, Johannes 4 de Carvalho-Segundo, Washington 4 Gabbay, Michael J. 4 Ghica, Dan R. 4 Hüttel, Hans 4 Keshvardoost, Khadijeh 4 Kozen, Dexter C. 4 Kutz, Yunus D. K. 4 Petrisan, Daniela Luan 4 Pientka, Brigitte 4 Sammartino, Matteo 4 Schröder, Lutz 4 Silva, Alexandra 4 Triebel, Hans 4 Volosivets, Sergeĭ Sergeevich 3 Aceto, Luca 3 Alexandru, Andrei 3 Bojańczyk, Mikołaj 3 Borgström, Johannes 3 Cardelli, Luca 3 Ciobanu, Gabriel 3 Clouston, Ranald A. 3 Copello, Ernesto 3 Crole, Roy L. 3 Degano, Pierpaolo 3 Fábregas, Ignacio 3 Fiore, Marcelo P. 3 García-Pérez, Álvaro 3 Golubov, Boris Ivanovich 3 Guliyev, Vagif Sabir 3 Hofmann, Martin 3 Ingólfsdóttir, Anna 3 Kikuchi, Kentaro 3 Lenglet, Sergueï 3 Levy, Jordi 3 Ligun, A. A. 3 Lybech, Stian 3 Mahmoudi, Mojgan 3 Miculan, Marino 3 Moerman, Joshua 3 Oswald, Peter 3 Popescu, Andrei 3 Ramazanov, Abdul-Rashid Kekhrimanovich 3 Reniers, Michel Adriaan 3 Schmitt, Alan 3 Shinwell, Mark R. 3 Silva, Gabriel Ferreira 3 Staton, Sam 3 Szasz, Nora 3 Taha, Walid 3 Tasistro, Alvaro 3 Traytel, Dmitry 3 Urban, Christian 3 Victor, Björn 3 Villaret, Mateu 2 Adámek, Jiří 2 Akhobadze, T. I. 2 Ancona, Davide 2 Aoto, Takahito 2 Balco, Samuel 2 Baumgartner, Alexander 2 Bavrin, Ivan Ivanovich 2 Belov, Aleksandr S. 2 Bengtson, Jesper 2 Benton, Nick 2 Bergstra, Jan A. 2 Brunet, Paul 2 Ciaffaglione, Alberto 2 Dolzhenko, Evgeniĭ Prokof’evich 2 Domínguez, Jesús Emilio 2 Dzhrbashyan, Mkhitar Mkrtichevich 2 Gadducci, Fabio 2 Gallego Arias, Emilio Jesús 2 Gardner, Philippa Anne 2 Gevorkyan, Gegham G. 2 Ghelli, Giorgio 2 Gheri, Lorenzo 2 Giannini, Paola 2 Grabowski, Janusz 2 Harper, Robert ...and 445 more Authors all top 5 Cited in 52 Serials 159 Analysis Mathematica 21 Theoretical Computer Science 20 Information and Computation 18 Journal of Automated Reasoning 12 Acta Mathematica Hungarica 12 Mathematical Structures in Computer Science 12 Logical Methods in Computer Science 10 Russian Mathematical Surveys 9 Transformation Groups 7 Journal of Functional Programming 6 Journal of Logical and Algebraic Methods in Programming 5 Journal of Computer and System Sciences 4 Applied Mathematics and Mechanics. (English Edition) 3 The Journal of Symbolic Logic 3 Annals of Pure and Applied Logic 3 Journal of Symbolic Computation 3 Formal Aspects of Computing 3 Higher-Order and Symbolic Computation 2 Acta Informatica 2 Fuzzy Sets and Systems 2 Publications Mathématiques 2 Acta Mathematicae Applicatae Sinica. English Series 2 The Journal of Logic and Algebraic Programming 2 Theory and Practice of Logic Programming 2 ACM Transactions on Computational Logic 2 Journal of Applied Logic 2 Categories and General Algebraic Structures with Applications 1 Archive for Rational Mechanics and Analysis 1 Astrophysics and Space Science 1 Journal d’Analyse Mathématique 1 Zhurnal Vychislitel’noĭ Matematiki i Matematicheskoĭ Fiziki 1 Semigroup Forum 1 Studia Logica 1 Bulletin of the Section of Logic 1 Distributed Computing 1 Archive for Mathematical Logic 1 Indagationes Mathematicae. New Series 1 Analele Științifice ale Universității Al. I. Cuza din Iași. Serie Nouă. Matematică 1 Formal Methods in System Design 1 Journal of Applied Non-Classical Logics 1 The Bulletin of Symbolic Logic 1 Theory of Computing Systems 1 Soft Computing 1 Journal of the ACM 1 Journal of Group Theory 1 RAIRO. Theoretical Informatics and Applications 1 Fundamenta Informaticae 1 Computer Languages, Systems & Structures 1 Vestnik Yuzhno-Ural’skogo Gosudarstvennogo Universiteta. Seriya Matematicheskoe Modelirovanie i Programmirovanie 1 Discrete Mathematics, Algorithms and Applications 1 Uchenye Zapiski Kazanskogo Universiteta. Seriya Fiziko-Matematicheskie Nauki 1 Vestnik Yuzhno-Ural’skogo Gosudarstvennogo Universiteta. Seriya Matematika. Mekhanika. Fizika all top 5 Cited in 50 Fields 256 Computer science (68-XX) 113 Mathematical logic and foundations (03-XX) 79 Harmonic analysis on Euclidean spaces (42-XX) 47 Approximations and expansions (41-XX) 29 Functional analysis (46-XX) 25 Category theory; homological algebra (18-XX) 21 Functions of a complex variable (30-XX) 11 Real functions (26-XX) 9 General algebraic systems (08-XX) 9 Sequences, series, summability (40-XX) 8 Group theory and generalizations (20-XX) 7 Partial differential equations (35-XX) 7 Probability theory and stochastic processes (60-XX) 6 Algebraic geometry (14-XX) 6 Measure and integration (28-XX) 6 Operator theory (47-XX) 5 Order, lattices, ordered algebraic structures (06-XX) 5 Game theory, economics, finance, and other social and behavioral sciences (91-XX) 4 Mechanics of deformable solids (74-XX) 4 Quantum theory (81-XX) 3 History and biography (01-XX) 3 Number theory (11-XX) 3 Potential theory (31-XX) 3 Several complex variables and analytic spaces (32-XX) 3 General topology (54-XX) 3 Global analysis, analysis on manifolds (58-XX) 3 Numerical analysis (65-XX) 2 Associative rings and algebras (16-XX) 2 Nonassociative rings and algebras (17-XX) 2 Topological groups, Lie groups (22-XX) 2 Ordinary differential equations (34-XX) 2 Abstract harmonic analysis (43-XX) 2 Integral equations (45-XX) 2 Differential geometry (53-XX) 2 Relativity and gravitational theory (83-XX) 2 Operations research, mathematical programming (90-XX) 1 General and overarching topics; collections (00-XX) 1 Combinatorics (05-XX) 1 Commutative algebra (13-XX) 1 Special functions (33-XX) 1 Dynamical systems and ergodic theory (37-XX) 1 Integral transforms, operational calculus (44-XX) 1 Calculus of variations and optimal control; optimization (49-XX) 1 Manifolds and cell complexes (57-XX) 1 Statistics (62-XX) 1 Mechanics of particles and systems (70-XX) 1 Fluid mechanics (76-XX) 1 Statistical mechanics, structure of matter (82-XX) 1 Biology and other natural sciences (92-XX) 1 Information and communication theory, circuits (94-XX) Citations by Year