Edit Profile (opens in new tab) Kawakami, Tatsuki Co-Author Distance Author ID: kawakami.tatsuki Published as: Kawakami, Tatsuki; Kawakami, T. External Links: ORCID Documents Indexed: 49 Publications since 1984, including 4 Additional arXiv Preprints 1 Contribution as Editor Co-Authors: 30 Co-Authors with 41 Joint Publications 713 Co-Co-Authors all top 5 Co-Authors 5 single-authored 26 Ishige, Kazuhiro 11 Fila, Marek 2 Fujishima, Yohei 2 Furioli, Giulia 2 Hasegawa, Shoichi 2 Ikoma, Norihisa 2 Kobayashi, Kanako 2 Lankeit, Johannes 2 Okabe, Shinya 2 Sire, Yannick 2 Terraneo, Elide 1 Ferone, Vincenzo 1 Ioku, Norisuke 1 Ishiwata, Michinori 1 Iwabuchi, Tsukasa 1 Jleli, Mohamed Boussairi 1 Kabeya, Yoshitsugu 1 Kobayashi, Mineo 1 Kobayashi, Shoichi 1 Kosaka, Atsushi 1 Michihisa, Hironori 1 Muratori, Matteo 1 Ninomiya, Hirokazu 1 Nishimura, Naoshi 1 Ohno, Nobutada 1 Ruf, Bernhard 1 Sakaguchi, Shigeru 1 Salani, Paolo 1 Samet, Bessem 1 Sato, Keijin 1 Sierżȩga, Mikołaj 1 Sugiyama, Yoshie 1 Takahashi, Futoshi 1 Takeda, Hiroshi 1 Ueda, Yoshihiro 1 Yamamoto, Sumio all top 5 Serials 3 Journal of Differential Equations 3 Calculus of Variations and Partial Differential Equations 3 Communications on Pure and Applied Analysis 2 Journal of Mathematical Analysis and Applications 2 Indiana University Mathematics Journal 2 Nonlinear Analysis. Theory, Methods & Applications. Series A: Theory and Methods 2 Asymptotic Analysis 1 Journal d’Analyse Mathématique 1 ZAMP. Zeitschrift für angewandte Mathematik und Physik 1 Annali di Matematica Pura ed Applicata. Serie Quarta 1 Funkcialaj Ekvacioj. Serio Internacia 1 International Journal for Numerical Methods in Engineering 1 Kodai Mathematical Journal 1 Mathematische Annalen 1 Annales de l’Institut Henri Poincaré. Analyse Non Linéaire 1 Computational Mechanics 1 Differential and Integral Equations 1 Applied Mathematical Modelling 1 Journal de Mathématiques Pures et Appliquées. Neuvième Série 1 SIAM Journal on Mathematical Analysis 1 Advances in Mathematical Sciences and Applications 1 NoDEA. Nonlinear Differential Equations and Applications 1 Advances in Differential Equations 1 Discrete and Continuous Dynamical Systems 1 Revista Matemática Complutense 1 Communications in Contemporary Mathematics 1 Journal of Evolution Equations 1 Discrete and Continuous Dynamical Systems. Series S 1 Springer INdAM Series 1 Journal of Elliptic and Parabolic Equations 1 SN Partial Differential Equations and Applications all top 5 Fields 42 Partial differential equations (35-XX) 4 Global analysis, analysis on manifolds (58-XX) 3 Integral equations (45-XX) 3 Mechanics of deformable solids (74-XX) 2 Functional analysis (46-XX) 1 General and overarching topics; collections (00-XX) 1 Algebraic geometry (14-XX) 1 Special functions (33-XX) 1 Dynamical systems and ergodic theory (37-XX) 1 Operator theory (47-XX) 1 Numerical analysis (65-XX) 1 Mechanics of particles and systems (70-XX) 1 Fluid mechanics (76-XX) 1 Classical thermodynamics, heat transfer (80-XX) 1 Biology and other natural sciences (92-XX) Publications by Year all cited Publications top 5 cited Publications Citations contained in zbMATH Open 35 Publications have been cited 293 times in 150 Documents Cited by ▼ Year ▼ The decay of the solutions for the heat equation with a potential. Zbl 1196.35051 Ishige, Kazuhiro; Ishiwata, Michinori; Kawakami, Tatsuki 22 2009 Supersolutions for a class of nonlinear parabolic systems. Zbl 1338.35228 Ishige, Kazuhiro; Kawakami, Tatsuki; Sierżȩga, Mikołaj 22 2016 Convergence to the Poisson kernel for the Laplace equation with a nonlinear dynamical boundary condition. Zbl 1279.47092 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 22 2012 Global solutions for a nonlinear integral equation with a generalized heat kernel. Zbl 1288.45004 Ishige, Kazuhiro; Kawakami, Tatsuki; Kobayashi, Kanako 21 2014 Asymptotics for a nonlinear integral equation with a generalized heat kernel. Zbl 1333.45010 Ishige, Kazuhiro; Kawakami, Tatsuki; Kobayashi, Kanako 20 2014 Refined asymptotic profiles for a semilinear heat equation. Zbl 1252.35117 Ishige, Kazuhiro; Kawakami, Tatsuki 19 2012 Asymptotic behavior and decay estimates of the solutions for a nonlinear parabolic equation with exponential nonlinearity. Zbl 1361.35069 Furioli, Giulia; Kawakami, Tatsuki; Ruf, Bernhard; Terraneo, Elide 14 2017 Global solutions of the heat equation with a nonlinear boundary condition. Zbl 1213.35102 Ishige, Kazuhiro; Kawakami, Tatsuki 14 2010 Asymptotic profiles to the solutions for a nonlinear damped wave equation. Zbl 1299.35209 Kawakami, Tatsuki; Ueda, Yoshihiro 12 2013 Existence of positive solutions of a semilinear elliptic equation with a dynamical boundary condition. Zbl 1329.35156 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 10 2015 Large time behavior of solutions of a semilinear elliptic equation with a dynamical boundary condition. Zbl 1281.35051 Fila, M.; Ishige, K.; Kawakami, T. 10 2013 Asymptotic expansions of solutions of the Cauchy problem for nonlinear parabolic equations. Zbl 1282.35130 Ishige, Kazuhiro; Kawakami, Tatsuki 10 2013 Asymptotic behavior of solutions for some semilinear heat equations in \(\mathbb R^N\). Zbl 1173.35364 Ishige, Kazuhiro; Kawakami, Tatsuki 9 2009 Asymptotic expansions of solutions of fractional diffusion equations. Zbl 1372.35338 Ishige, Kazuhiro; Kawakami, Tatsuki; Michihisa, Hironori 9 2017 Critical behavior for a semilinear parabolic equation with forcing term depending on time and space. Zbl 1445.35062 Jleli, Mohamed; Kawakami, Tatsuki; Samet, Bessem 9 2020 Implicit integration and consistent tangent modulus of a time-dependent non-unified constitutive model. Zbl 1032.74670 Kobayashi, M.; Mukai, M.; Takahashi, H.; Ohno, N.; Kawakami, T.; Ishikawa, T. 8 2003 Uniqueness theorem on weak solutions to the Keller-Segel system of degenerate and singular types. Zbl 1336.35009 Kawakami, Tatsuki; Sugiyama, Yoshie 8 2016 Existence of solutions for a higher-order semilinear parabolic equation with singular initial data. Zbl 1454.35222 Ishige, Kazuhiro; Kawakami, Tatsuki; Okabe, Shinya 8 2020 Large-time behavior of small solutions of a two-dimensional semilinear elliptic equation with a dynamical boundary condition. Zbl 1280.35051 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 7 2013 Bifurcation sets and chaotic states of a gear system subject to harmonic excitation. Zbl 0737.70013 Sato, K.; Yamamoto, S.; Kawakami, T. 6 1991 Higher order asymptotic expansions to the solutions for a nonlinear damped wave equation. Zbl 1367.35063 Kawakami, Tatsuki; Takeda, Hiroshi 6 2016 An exterior nonlinear elliptic problem with a dynamical boundary condition. Zbl 1377.35111 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 5 2017 Minimal solutions of a semilinear elliptic equation with a dynamical boundary condition. Zbl 1344.35055 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 5 2016 Rate of convergence in the large diffusion limit for the heat equation with a dynamical boundary condition. Zbl 1433.35395 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki; Lankeit, Johannes 5 2019 Global existence of solutions for the heat equation with a nonlinear boundary condition. Zbl 1192.35105 Kawakami, Tatsuki 4 2010 Critical exponent for the global existence of solutions to a semilinear heat equation with degenerate coefficients. Zbl 1419.35122 Fujishima, Yohei; Kawakami, Tatsuki; Sire, Yannick 4 2019 Eigenvalues of the Laplace-Beltrami operator on a large spherical cap under the Robin problem. Zbl 1317.35152 Kabeya, Yoshitsugu; Kawakami, Tatsuki; Kosaka, Atsushi; Ninomiya, Hirokazu 3 2014 The large diffusion limit for the heat equation in the exterior of the unit ball with a dynamical boundary condition. Zbl 1446.35046 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki; Lankeit, Johannes 3 2020 Existence of solutions to nonlinear parabolic equations via majorant integral kernel. Zbl 1495.35096 Ishige, Kazuhiro; Kawakami, Tatsuki; Okabe, Shinya 3 2022 The large diffusion limit for the heat equation with a dynamical boundary condition. Zbl 1450.35031 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 2 2021 Critical Fujita exponents for semilinear heat equations with quadratically decaying potential. Zbl 1455.35012 Ishige, Kazuhiro; Kawakami, Tatsuki 2 2020 Nonexistence of radial optimal functions for the Sobolev inequality on Cartan-Hadamard manifolds. Zbl 1473.35013 Kawakami, Tatsuki; Muratori, Matteo 2 2021 Entropy dissipation method for the solutions of the heat equation with a nonlinear boundary condition. Zbl 1227.35171 Kawakami, Tatsuki 1 2010 Higher order asymptotic expansion for the heat equation with a nonlinear boundary condition. Zbl 1292.35083 Kawakami, Tatsuki 1 2014 On weak solutions to a fractional Hardy-Hénon equation. I: Nonexistence. Zbl 1466.35359 Hasegawa, Shoichi; Ikoma, Norihisa; Kawakami, Tatsuki 1 2021 Existence of solutions to nonlinear parabolic equations via majorant integral kernel. Zbl 1495.35096 Ishige, Kazuhiro; Kawakami, Tatsuki; Okabe, Shinya 3 2022 The large diffusion limit for the heat equation with a dynamical boundary condition. Zbl 1450.35031 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 2 2021 Nonexistence of radial optimal functions for the Sobolev inequality on Cartan-Hadamard manifolds. Zbl 1473.35013 Kawakami, Tatsuki; Muratori, Matteo 2 2021 On weak solutions to a fractional Hardy-Hénon equation. I: Nonexistence. Zbl 1466.35359 Hasegawa, Shoichi; Ikoma, Norihisa; Kawakami, Tatsuki 1 2021 Critical behavior for a semilinear parabolic equation with forcing term depending on time and space. Zbl 1445.35062 Jleli, Mohamed; Kawakami, Tatsuki; Samet, Bessem 9 2020 Existence of solutions for a higher-order semilinear parabolic equation with singular initial data. Zbl 1454.35222 Ishige, Kazuhiro; Kawakami, Tatsuki; Okabe, Shinya 8 2020 The large diffusion limit for the heat equation in the exterior of the unit ball with a dynamical boundary condition. Zbl 1446.35046 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki; Lankeit, Johannes 3 2020 Critical Fujita exponents for semilinear heat equations with quadratically decaying potential. Zbl 1455.35012 Ishige, Kazuhiro; Kawakami, Tatsuki 2 2020 Rate of convergence in the large diffusion limit for the heat equation with a dynamical boundary condition. Zbl 1433.35395 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki; Lankeit, Johannes 5 2019 Critical exponent for the global existence of solutions to a semilinear heat equation with degenerate coefficients. Zbl 1419.35122 Fujishima, Yohei; Kawakami, Tatsuki; Sire, Yannick 4 2019 Asymptotic behavior and decay estimates of the solutions for a nonlinear parabolic equation with exponential nonlinearity. Zbl 1361.35069 Furioli, Giulia; Kawakami, Tatsuki; Ruf, Bernhard; Terraneo, Elide 14 2017 Asymptotic expansions of solutions of fractional diffusion equations. Zbl 1372.35338 Ishige, Kazuhiro; Kawakami, Tatsuki; Michihisa, Hironori 9 2017 An exterior nonlinear elliptic problem with a dynamical boundary condition. Zbl 1377.35111 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 5 2017 Supersolutions for a class of nonlinear parabolic systems. Zbl 1338.35228 Ishige, Kazuhiro; Kawakami, Tatsuki; Sierżȩga, Mikołaj 22 2016 Uniqueness theorem on weak solutions to the Keller-Segel system of degenerate and singular types. Zbl 1336.35009 Kawakami, Tatsuki; Sugiyama, Yoshie 8 2016 Higher order asymptotic expansions to the solutions for a nonlinear damped wave equation. Zbl 1367.35063 Kawakami, Tatsuki; Takeda, Hiroshi 6 2016 Minimal solutions of a semilinear elliptic equation with a dynamical boundary condition. Zbl 1344.35055 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 5 2016 Existence of positive solutions of a semilinear elliptic equation with a dynamical boundary condition. Zbl 1329.35156 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 10 2015 Global solutions for a nonlinear integral equation with a generalized heat kernel. Zbl 1288.45004 Ishige, Kazuhiro; Kawakami, Tatsuki; Kobayashi, Kanako 21 2014 Asymptotics for a nonlinear integral equation with a generalized heat kernel. Zbl 1333.45010 Ishige, Kazuhiro; Kawakami, Tatsuki; Kobayashi, Kanako 20 2014 Eigenvalues of the Laplace-Beltrami operator on a large spherical cap under the Robin problem. Zbl 1317.35152 Kabeya, Yoshitsugu; Kawakami, Tatsuki; Kosaka, Atsushi; Ninomiya, Hirokazu 3 2014 Higher order asymptotic expansion for the heat equation with a nonlinear boundary condition. Zbl 1292.35083 Kawakami, Tatsuki 1 2014 Asymptotic profiles to the solutions for a nonlinear damped wave equation. Zbl 1299.35209 Kawakami, Tatsuki; Ueda, Yoshihiro 12 2013 Large time behavior of solutions of a semilinear elliptic equation with a dynamical boundary condition. Zbl 1281.35051 Fila, M.; Ishige, K.; Kawakami, T. 10 2013 Asymptotic expansions of solutions of the Cauchy problem for nonlinear parabolic equations. Zbl 1282.35130 Ishige, Kazuhiro; Kawakami, Tatsuki 10 2013 Large-time behavior of small solutions of a two-dimensional semilinear elliptic equation with a dynamical boundary condition. Zbl 1280.35051 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 7 2013 Convergence to the Poisson kernel for the Laplace equation with a nonlinear dynamical boundary condition. Zbl 1279.47092 Fila, Marek; Ishige, Kazuhiro; Kawakami, Tatsuki 22 2012 Refined asymptotic profiles for a semilinear heat equation. Zbl 1252.35117 Ishige, Kazuhiro; Kawakami, Tatsuki 19 2012 Global solutions of the heat equation with a nonlinear boundary condition. Zbl 1213.35102 Ishige, Kazuhiro; Kawakami, Tatsuki 14 2010 Global existence of solutions for the heat equation with a nonlinear boundary condition. Zbl 1192.35105 Kawakami, Tatsuki 4 2010 Entropy dissipation method for the solutions of the heat equation with a nonlinear boundary condition. Zbl 1227.35171 Kawakami, Tatsuki 1 2010 The decay of the solutions for the heat equation with a potential. Zbl 1196.35051 Ishige, Kazuhiro; Ishiwata, Michinori; Kawakami, Tatsuki 22 2009 Asymptotic behavior of solutions for some semilinear heat equations in \(\mathbb R^N\). Zbl 1173.35364 Ishige, Kazuhiro; Kawakami, Tatsuki 9 2009 Implicit integration and consistent tangent modulus of a time-dependent non-unified constitutive model. Zbl 1032.74670 Kobayashi, M.; Mukai, M.; Takahashi, H.; Ohno, N.; Kawakami, T.; Ishikawa, T. 8 2003 Bifurcation sets and chaotic states of a gear system subject to harmonic excitation. Zbl 0737.70013 Sato, K.; Yamamoto, S.; Kawakami, T. 6 1991 all cited Publications top 5 cited Publications all top 5 Cited by 166 Authors 32 Ishige, Kazuhiro 22 Kawakami, Tatsuki 11 Fujishima, Yohei 8 Takeda, Hiroshi 7 Fila, Marek 6 Hisa, Kotaro 6 Wakasugi, Yuta 4 Ikehata, Ryo 4 Ioku, Norisuke 4 Li, Fengjie 4 Liu, Bingchen 4 Okabe, Shinya 4 Takahashi, Jin 4 Terraneo, Elide 4 Yamamoto, Masakazu 3 Eom, Junyong 3 Hamamuki, Nao 3 Harada, Junichi 3 Ishiwata, Michinori 3 Kabeya, Yoshitsugu 3 Majdoub, Mohamed 3 Miyake, Nobuhito 3 Nguyen, Anh-Tuan 3 Ruf, Bernhard 3 Suzuki, Masamitsu 2 Braga, Gastão A. 2 Chen, Alatancang 2 Colli, Pierluigi 2 Ferreira, Lucas Catão de Freitas 2 Fino, Ahmad Z. 2 Fujiwara, Kazumasa 2 Fukao, Takeshi 2 Furioli, Giulia 2 Furtado, Marcelo Fernandes 2 Huang, Junjie 2 Ikeda, Masahiro 2 Jleli, Mohamed Boussairi 2 Kobayashi, Kanako 2 Laister, Robert 2 Liu, Jianguo 2 Liu, Qing 2 Michihisa, Hironori 2 Miyamoto, Yasuhito 2 Moreira, Jussara M. 2 Nguyen Huy Tuan 2 Samet, Bessem 2 Sobajima, Motohiro 2 Souza, Camila F. 2 Sugiyama, Yuusuke 2 Sun, Xizheng 2 Taliaferro, Steven D. 2 Wang, Jinhuan 2 Xie, Minghong 2 Xu, Jing 1 Abiko, Keisuke 1 Alessa, Rasha 1 Aljaber, Noha 1 Alshehri, Aisha 1 Altamimi, Haya 1 Alzahrani, Ebraheem O. 1 Bandle, Catherine 1 Bonet Solves, José 1 Borikhanov, Meiirkhan B. 1 Can, Nguyen Huu 1 Caraballo Garrido, Tomás 1 Cárdenas, Armando S. 1 Castillo, Ricardo 1 Chen, Wenhui 1 Dao, Tuan Anh 1 de Almeida, Marcelo Fernandes 1 de Sousa, Karla Carolina Vicente 1 Deng, Yanhua 1 Du, Chengxin 1 Egashira, Takanari 1 Fetecau, Razvan C. 1 Fujii, Mikihiro 1 Georgiev, Vladimir S. 1 Giga, Yoshikazu 1 Giraudon, Théo 1 Greco, Antonio 1 Grunau, Hans-Christoph 1 Guzmán-Rea, Omar 1 Gvelesiani, Simon 1 Hasegawa, Shoichi 1 He, Jiawei 1 Hong, Liang 1 Huang, Hui 1 Iannizzotto, Antonio 1 Ikoma, Norihisa 1 Inui, Takahisa 1 Ishii, Hitoshi 1 Iwabuchi, Tsukasa 1 Kim, Sunghoon 1 Kirane, Mokhtar 1 Kusaba, Ryunosuke 1 Lankeit, Johannes 1 Latorre, Marta 1 Lee, Ki-Ahm 1 Li, Chunyi 1 Li, Ke ...and 66 more Authors all top 5 Cited in 60 Serials 13 Journal of Mathematical Analysis and Applications 12 Journal of Differential Equations 11 Nonlinear Analysis. Theory, Methods & Applications. Series A: Theory and Methods 7 SN Partial Differential Equations and Applications 6 Journal of Evolution Equations 5 Mathematische Annalen 5 Calculus of Variations and Partial Differential Equations 5 Discrete and Continuous Dynamical Systems 4 Annales de l’Institut Henri Poincaré. Analyse Non Linéaire 4 NoDEA. Nonlinear Differential Equations and Applications 4 Nonlinear Analysis. Real World Applications 3 Mathematical Methods in the Applied Sciences 3 Journal of the Mathematical Society of Japan 3 Applied Mathematics Letters 3 Asymptotic Analysis 3 Journal de Mathématiques Pures et Appliquées. Neuvième Série 3 SIAM Journal on Mathematical Analysis 3 Communications on Pure and Applied Analysis 2 Journal d’Analyse Mathématique 2 Journal of Mathematical Physics 2 Revista Matemática Complutense 2 Differential Equations and Applications 2 Advances in Nonlinear Analysis 2 Journal of Elliptic and Parabolic Equations 1 Nonlinearity 1 ZAMP. Zeitschrift für angewandte Mathematik und Physik 1 Chaos, Solitons and Fractals 1 Funkcialaj Ekvacioj. Serio Internacia 1 Journal of Computational and Applied Mathematics 1 Mathematische Nachrichten 1 Osaka Journal of Mathematics 1 Rendiconti dell’Istituto di Matematica dell’Università di Trieste 1 Tokyo Journal of Mathematics 1 Transactions of the American Mathematical Society 1 Chinese Annals of Mathematics. Series A 1 Acta Applicandae Mathematicae 1 The Journal of Geometric Analysis 1 Communications in Partial Differential Equations 1 Proceedings of the Royal Society of Edinburgh. Section A. Mathematics 1 Stochastic Processes and their Applications 1 Journal of Dynamics and Differential Equations 1 Potential Analysis 1 Bulletin of the Belgian Mathematical Society - Simon Stevin 1 Bulletin des Sciences Mathématiques 1 Opuscula Mathematica 1 Boletín de la Sociedad Matemática Mexicana. Third Series 1 European Series in Applied and Industrial Mathematics (ESAIM): Control, Optimization and Calculus of Variations 1 Journal of Mathematical Fluid Mechanics 1 Acta Mathematica Sinica. English Series 1 Communications in Nonlinear Science and Numerical Simulation 1 Communications in Contemporary Mathematics 1 Acta Mathematica Scientia. Series B. (English Edition) 1 Journal of Applied Mathematics and Computing 1 Annali della Scuola Normale Superiore di Pisa. Classe di Scienze. Serie V 1 Boundary Value Problems 1 Discrete and Continuous Dynamical Systems. Series S 1 Stochastic and Partial Differential Equations. Analysis and Computations 1 Evolution Equations and Control Theory 1 Electronic Research Archive 1 La Matematica all top 5 Cited in 22 Fields 149 Partial differential equations (35-XX) 10 Functional analysis (46-XX) 9 Biology and other natural sciences (92-XX) 8 Integral equations (45-XX) 5 Special functions (33-XX) 5 Mechanics of deformable solids (74-XX) 4 Real functions (26-XX) 4 Global analysis, analysis on manifolds (58-XX) 3 Ordinary differential equations (34-XX) 3 Operator theory (47-XX) 3 Calculus of variations and optimal control; optimization (49-XX) 3 Probability theory and stochastic processes (60-XX) 3 Classical thermodynamics, heat transfer (80-XX) 2 Differential geometry (53-XX) 2 Numerical analysis (65-XX) 2 Fluid mechanics (76-XX) 1 Harmonic analysis on Euclidean spaces (42-XX) 1 Optics, electromagnetic theory (78-XX) 1 Quantum theory (81-XX) 1 Statistical mechanics, structure of matter (82-XX) 1 Relativity and gravitational theory (83-XX) 1 Geophysics (86-XX) Citations by Year