Edit Profile (opens in new tab) Godoy, Tomás F. Compute Distance To: Compute Author ID: godoy.tomas-f Published as: Godoy, T.; Godoy, Tomas; Godoy, Tomás; Godoy, Tomás F. Documents Indexed: 67 Publications since 1993 Co-Authors: 13 Co-Authors with 63 Joint Publications 107 Co-Co-Authors all top 5 Co-Authors 3 single-authored 18 Paczka, Sofia R. 16 Kaufmann, Uriel 15 Urciuolo, Marta Susana 10 Ferreyra, Elida V. 10 Guerin, Alfredo J. 8 Gossez, Jean-Pierre 7 Saal, Linda V. 3 Lami Dozo, Enrique J. 2 Aranda, Carlos Cesar 2 Rocha, Pablo Alejandro 1 Lami, Dozo E. 1 Miatello, Roberto Jorge 1 Williams, Floyd L. all top 5 Serials 7 Colloquium Mathematicum 6 Electronic Journal of Differential Equations (EJDE) 5 Mathematica Scandinavica 4 Electronic Journal of Qualitative Theory of Differential Equations 4 AIMS Mathematics 3 Journal of Mathematical Analysis and Applications 3 Studia Mathematica 3 Nonlinear Analysis. Theory, Methods & Applications. Series A: Theory and Methods 3 Differential and Integral Equations 2 Rendiconti dell’Istituto di Matematica dell’Università di Trieste 2 Revista de la Unión Matemática Argentina 2 Acta Mathematica Hungarica 2 NoDEA. Nonlinear Differential Equations and Applications 2 Discrete and Continuous Dynamical Systems 2 Abstract and Applied Analysis 1 Bulletin of the Australian Mathematical Society 1 Houston Journal of Mathematics 1 Journal of Geometry and Physics 1 Annali di Matematica Pura ed Applicata. Serie Quarta 1 Czechoslovak Mathematical Journal 1 Mathematische Zeitschrift 1 Pacific Journal of Mathematics 1 Rendiconti del Seminario Matematico della Università di Padova 1 Rendiconti del Seminario Matematico 1 Publicacions Matemàtiques 1 Advances in Mathematical Sciences and Applications 1 Calculus of Variations and Partial Differential Equations 1 The Journal of Fourier Analysis and Applications 1 RIMS Kokyuroku 1 JIPAM. Journal of Inequalities in Pure & Applied Mathematics 1 Advanced Nonlinear Studies 1 Complex Variables and Elliptic Equations all top 5 Fields 46 Partial differential equations (35-XX) 16 Harmonic analysis on Euclidean spaces (42-XX) 9 Operator theory (47-XX) 7 Abstract harmonic analysis (43-XX) 5 Topological groups, Lie groups (22-XX) 3 Integral transforms, operational calculus (44-XX) 3 Functional analysis (46-XX) 1 Real functions (26-XX) 1 Integral equations (45-XX) 1 Calculus of variations and optimal control; optimization (49-XX) 1 Differential geometry (53-XX) 1 Global analysis, analysis on manifolds (58-XX) 1 Quantum theory (81-XX) Publications by Year all cited Publications top 5 cited Publications Citations contained in zbMATH Open 45 Publications have been cited 157 times in 107 Documents Cited by ▼ Year ▼ On the antimaximum principle for the \(p\)-Laplacian with indefinite weight. Zbl 1157.35445Godoy, T.; Gossez, J.-P.; Paczka, S. 26 2002 On strictly positive solutions for some semilinear elliptic problems. Zbl 1348.35070Godoy, T.; Kaufmann, U. 9 2013 Existence of strictly positive solutions for sublinear elliptic problems in bounded domains. Zbl 1301.35018Godoy, T.; Kaufmann, U. 8 2014 Antimaximum principle for elliptic problems with weight. Zbl 0920.35045Godoy, T.; Gossez, J.-P.; Paczka, S. 7 1999 On certain integral operators of fractional type. Zbl 0937.47032Godoy, T.; Urciuolo, M. 7 1999 On Dirichlet problems with singular nonlinearity of indefinite sign. Zbl 1318.35050Godoy, T.; Kaufmann, U. 7 2015 Existence and multiplicity of positive solutions for a singular problem associated to the \(p\)-Laplacian operator. Zbl 1129.35365Aranda, Carlos; Godoy, Tomas 6 2004 About the \(L^ p\)-boundedness of some integral operators. Zbl 0819.42006Godoy, T.; Urciuolo, M. 6 1993 On principal eigenvalues for periodic parabolic problems with optimal condition on the weight function. Zbl 0988.35067Godoy, T.; Kaufmann, U. 6 2001 A minimax formula for the principal eigenvalues of Dirichlet problems and its applications. Zbl 1153.35057Godoy, Tomas; Gossez, Jean-Pierre; Paczka, Sofia R. 6 2007 The period parabolic eigenvalue problem with \(L^ \infty\) weight. Zbl 0892.35071Godoy, T.; Lami, Dozo E.; Paczka, S. 5 1997 Existence of nonnegative solutions to singular elliptic problems, a variational approach. Zbl 1401.35110Godoy, Tomas; Guerin, Alfredo 4 2018 Boundedness properties of some convolution operators with singular measures. Zbl 0934.42009Ferreyra, E.; Godoy, T.; Urciuolo, M. 4 1997 On the asymptotic behavior of the principal eigenvalues of some elliptic problems. Zbl 1205.35172Godoy, Tomas; Gossez, Jean-Pierre; Paczka, Sofia 4 2010 Endpoint bounds for convolution operators with singular measures. Zbl 0915.42009Ferreyra, E.; Godoy, T.; Urciuolo, M. 3 1998 On the existence of positive solutions for periodic parabolic sublinear problems. Zbl 1133.35380Godoy, T.; Kaufmann, U. 3 2003 Periodic parabolic problems with nonlinearities indefinite in sign. Zbl 1146.35051Godoy, T.; Kaufmann, U. 3 2007 Sharp \(L^p-L^q\) estimates for singular fractional integral operators. Zbl 0973.42006Ferreyra, E.; Godoy, T.; Urciuolo, M. 3 1999 On positive solutions for some semilinear periodic parabolic eigenvalue problems. Zbl 1091.35036Godoy, T.; Kaufmann, U. 3 2003 Existence of nonnegative solutions for singular elliptic problems. Zbl 1344.35051Godoy, Tomas; Guerin, Alfredo J. 3 2016 Multiplicity of positive weak solutions to subcritical singular elliptic Dirichlet problems. Zbl 1413.35227Godoy, Tomas; Guerin, Alfredo 2 2017 About certain singular kernels \(K(x,y)=K_ 1(x-y)K_ 2(x+y)\). Zbl 0822.42009Godoy, Tomás; Saal, Linda; Urciuolo, Marta 2 1994 \(L^p\)-\(L^q\) estimates for convolution operators with \(n\)-dimensional singular measures. Zbl 0928.42004Ferreyra, E.; Godoy, T.; Urciuolo, M. 2 1997 \(L^2\) spectral decomposition on the Heisenberg group associated to the action of \(\text{U}(p,q)\). Zbl 1009.43005Godoy, T.; Saal, L. 2 2000 A minimax formula for principal eigenvalues and application to an antimaximum principle. Zbl 1097.35040Godoy, T.; Gossez, J.-P.; Paczka, S. 2 2004 On the principal eigenvalues of some elliptic problems with large drift. Zbl 1259.35152Godoy, Tomas; Gossez, Jean-Pierre; Paczka, Sofia 2 2013 About the \(L^ p\)-boundedness of integral operators with kernels of the form \(K_ 1(x-y)K_ 2(x+y)\). Zbl 0874.42010Godoy, T.; Urciuolo, M. 2 1996 Multiple finite-energy positive weak solutions to singular elliptic problems with a parameter. Zbl 1434.35013Godoy, Tomas; Guerin, Alfredo 2 2018 A semilinear singular problem for the fractional Laplacian. Zbl 1427.35319Godoy, Tomas 2 2018 Corrigendum to Multiplicity of positive weak solutions to subcritical singular elliptic Dirichlet problems. Zbl 1413.35228Godoy, Tomas; Guerin, Alfredo 1 2018 Convolution operators with fractional measures associated to holomorphic functions. Zbl 0995.42010Ferreyra, E.; Godoy, T.; Urciuolo, M. 1 2001 On a nonlinear Dirichlet problem with a singularity along the boundary. Zbl 1021.35029Aranda, C.; Godoy, T. 1 2002 On positive solutions of some periodic parabolic eigenvalue problem with a weight function. Zbl 0937.35005Godoy, T.; Guerin, A.; Paczka, S. 1 1999 On some singular periodic parabolic problems. Zbl 1077.35008Godoy, T.; Hernández, J.; Kaufmann, U.; Paczka, S. 1 2005 Inhomogeneous periodic parabolic problems with indefinite data. Zbl 1242.35134Godoy, T.; Kaufmann, U. 1 2011 The type set for homogeneous singular measures on \({\mathbb R}^3\) of polynomial type. Zbl 1146.42002Ferreyra, E.; Godoy, T.; Urciuolo, M. 1 2006 A spherical transform on Schwartz functions on the Heisenberg group associated to the action of \(U(p,q)\). Zbl 1115.43005Godoy, T.; Saal, L. 1 2006 The local zeta function for symmetric spaces of non-compact type. Zbl 1218.58026Godoy, Tomás F.; Miatello, Roberto J.; Williams, Floyd L. 1 2011 On the spectrum of the generalized Gelfand pair \((U(p,q),H_n)\), \(p+q=n\). Zbl 1190.22011Godoy, Tomás; Saal, Linda 1 2009 On the antimaximum principle for parabolic periodic problems with weight. Zbl 1098.35069Lami Dozo, E.; Godoy, T.; Paczka, S. 1 2002 On the relative fundamental solutions for a second order differential operator on the Heisenberg group. Zbl 0974.43002Godoy, T.; Saal, L. 1 2001 On the limit behavior in a free boundary model for the diffusion in a polymer. Zbl 1152.35320Gaudiano, M.; Godoy, T.; Turner, C. 1 2007 Regularity of the lower positive branch for singular elliptic bifurcation problems. Zbl 1418.35187Godoy, Tomas; Guerin, Alfredo 1 2019 Existence and multiplicity of solutions to superlinear periodic parabolic problems. Zbl 1390.35118Godoy, Tomas; Kaufmann, Uriel 1 2018 Positive weak solutions of elliptic Dirichlet problems with singularities in both the dependent and the independent variables. Zbl 1438.35186Godoy, Tomas; Guerin, Alfredo 1 2019 Regularity of the lower positive branch for singular elliptic bifurcation problems. Zbl 1418.35187Godoy, Tomas; Guerin, Alfredo 1 2019 Positive weak solutions of elliptic Dirichlet problems with singularities in both the dependent and the independent variables. Zbl 1438.35186Godoy, Tomas; Guerin, Alfredo 1 2019 Existence of nonnegative solutions to singular elliptic problems, a variational approach. Zbl 1401.35110Godoy, Tomas; Guerin, Alfredo 4 2018 Multiple finite-energy positive weak solutions to singular elliptic problems with a parameter. Zbl 1434.35013Godoy, Tomas; Guerin, Alfredo 2 2018 A semilinear singular problem for the fractional Laplacian. Zbl 1427.35319Godoy, Tomas 2 2018 Corrigendum to Multiplicity of positive weak solutions to subcritical singular elliptic Dirichlet problems. Zbl 1413.35228Godoy, Tomas; Guerin, Alfredo 1 2018 Existence and multiplicity of solutions to superlinear periodic parabolic problems. Zbl 1390.35118Godoy, Tomas; Kaufmann, Uriel 1 2018 Multiplicity of positive weak solutions to subcritical singular elliptic Dirichlet problems. Zbl 1413.35227Godoy, Tomas; Guerin, Alfredo 2 2017 Existence of nonnegative solutions for singular elliptic problems. Zbl 1344.35051Godoy, Tomas; Guerin, Alfredo J. 3 2016 On Dirichlet problems with singular nonlinearity of indefinite sign. Zbl 1318.35050Godoy, T.; Kaufmann, U. 7 2015 Existence of strictly positive solutions for sublinear elliptic problems in bounded domains. Zbl 1301.35018Godoy, T.; Kaufmann, U. 8 2014 On strictly positive solutions for some semilinear elliptic problems. Zbl 1348.35070Godoy, T.; Kaufmann, U. 9 2013 On the principal eigenvalues of some elliptic problems with large drift. Zbl 1259.35152Godoy, Tomas; Gossez, Jean-Pierre; Paczka, Sofia 2 2013 Inhomogeneous periodic parabolic problems with indefinite data. Zbl 1242.35134Godoy, T.; Kaufmann, U. 1 2011 The local zeta function for symmetric spaces of non-compact type. Zbl 1218.58026Godoy, Tomás F.; Miatello, Roberto J.; Williams, Floyd L. 1 2011 On the asymptotic behavior of the principal eigenvalues of some elliptic problems. Zbl 1205.35172Godoy, Tomas; Gossez, Jean-Pierre; Paczka, Sofia 4 2010 On the spectrum of the generalized Gelfand pair \((U(p,q),H_n)\), \(p+q=n\). Zbl 1190.22011Godoy, Tomás; Saal, Linda 1 2009 A minimax formula for the principal eigenvalues of Dirichlet problems and its applications. Zbl 1153.35057Godoy, Tomas; Gossez, Jean-Pierre; Paczka, Sofia R. 6 2007 Periodic parabolic problems with nonlinearities indefinite in sign. Zbl 1146.35051Godoy, T.; Kaufmann, U. 3 2007 On the limit behavior in a free boundary model for the diffusion in a polymer. Zbl 1152.35320Gaudiano, M.; Godoy, T.; Turner, C. 1 2007 The type set for homogeneous singular measures on \({\mathbb R}^3\) of polynomial type. Zbl 1146.42002Ferreyra, E.; Godoy, T.; Urciuolo, M. 1 2006 A spherical transform on Schwartz functions on the Heisenberg group associated to the action of \(U(p,q)\). Zbl 1115.43005Godoy, T.; Saal, L. 1 2006 On some singular periodic parabolic problems. Zbl 1077.35008Godoy, T.; Hernández, J.; Kaufmann, U.; Paczka, S. 1 2005 Existence and multiplicity of positive solutions for a singular problem associated to the \(p\)-Laplacian operator. Zbl 1129.35365Aranda, Carlos; Godoy, Tomas 6 2004 A minimax formula for principal eigenvalues and application to an antimaximum principle. Zbl 1097.35040Godoy, T.; Gossez, J.-P.; Paczka, S. 2 2004 On the existence of positive solutions for periodic parabolic sublinear problems. Zbl 1133.35380Godoy, T.; Kaufmann, U. 3 2003 On positive solutions for some semilinear periodic parabolic eigenvalue problems. Zbl 1091.35036Godoy, T.; Kaufmann, U. 3 2003 On the antimaximum principle for the \(p\)-Laplacian with indefinite weight. Zbl 1157.35445Godoy, T.; Gossez, J.-P.; Paczka, S. 26 2002 On a nonlinear Dirichlet problem with a singularity along the boundary. Zbl 1021.35029Aranda, C.; Godoy, T. 1 2002 On the antimaximum principle for parabolic periodic problems with weight. Zbl 1098.35069Lami Dozo, E.; Godoy, T.; Paczka, S. 1 2002 On principal eigenvalues for periodic parabolic problems with optimal condition on the weight function. Zbl 0988.35067Godoy, T.; Kaufmann, U. 6 2001 Convolution operators with fractional measures associated to holomorphic functions. Zbl 0995.42010Ferreyra, E.; Godoy, T.; Urciuolo, M. 1 2001 On the relative fundamental solutions for a second order differential operator on the Heisenberg group. Zbl 0974.43002Godoy, T.; Saal, L. 1 2001 \(L^2\) spectral decomposition on the Heisenberg group associated to the action of \(\text{U}(p,q)\). Zbl 1009.43005Godoy, T.; Saal, L. 2 2000 Antimaximum principle for elliptic problems with weight. Zbl 0920.35045Godoy, T.; Gossez, J.-P.; Paczka, S. 7 1999 On certain integral operators of fractional type. Zbl 0937.47032Godoy, T.; Urciuolo, M. 7 1999 Sharp \(L^p-L^q\) estimates for singular fractional integral operators. Zbl 0973.42006Ferreyra, E.; Godoy, T.; Urciuolo, M. 3 1999 On positive solutions of some periodic parabolic eigenvalue problem with a weight function. Zbl 0937.35005Godoy, T.; Guerin, A.; Paczka, S. 1 1999 Endpoint bounds for convolution operators with singular measures. Zbl 0915.42009Ferreyra, E.; Godoy, T.; Urciuolo, M. 3 1998 The period parabolic eigenvalue problem with \(L^ \infty\) weight. Zbl 0892.35071Godoy, T.; Lami, Dozo E.; Paczka, S. 5 1997 Boundedness properties of some convolution operators with singular measures. Zbl 0934.42009Ferreyra, E.; Godoy, T.; Urciuolo, M. 4 1997 \(L^p\)-\(L^q\) estimates for convolution operators with \(n\)-dimensional singular measures. Zbl 0928.42004Ferreyra, E.; Godoy, T.; Urciuolo, M. 2 1997 About the \(L^ p\)-boundedness of integral operators with kernels of the form \(K_ 1(x-y)K_ 2(x+y)\). Zbl 0874.42010Godoy, T.; Urciuolo, M. 2 1996 About certain singular kernels \(K(x,y)=K_ 1(x-y)K_ 2(x+y)\). Zbl 0822.42009Godoy, Tomás; Saal, Linda; Urciuolo, Marta 2 1994 About the \(L^ p\)-boundedness of some integral operators. Zbl 0819.42006Godoy, T.; Urciuolo, M. 6 1993 all cited Publications top 5 cited Publications all top 5 Cited by 127 Authors 18 Kaufmann, Uriel 17 Godoy, Tomás F. 14 Papageorgiou, Nikolaos S. 7 Ramos Quoirin, Humberto 7 Urciuolo, Marta Susana 6 Gossez, Jean-Pierre 6 Riveros, María Silvina 6 Umezu, Kenichiro 5 Paczka, Sofia R. 4 Ferreyra, Elida V. 4 Motreanu, Dumitru 4 Motreanu, Viorica Venera 3 Cuesta, Mabel 3 Firnkorn, Gonzalo H. Ibañez 3 Guerin, Alfredo J. 3 Oliva, Francescantonio 2 Arias, Margarita 2 Barletta, Giuseppina 2 Campos, Juan 2 Dakkak, Ahmed 2 De Coster, Colette 2 Drábek, Pavel 2 Fernández, Antonio J. 2 Flores, Guillermo Javier 2 Gasiński, Leszek 2 Greenblatt, Michael 2 Medri, Iván 2 Rocha, Pablo Alejandro 2 Sanhaji, Ahmed 2 Staicu, Vasile 2 Vidal, Raúl Emilio 1 Aizicovici, Sergiu 1 Alotaibi, Trad 1 Altenberg, Lee 1 Andrade Santos, Sandrina Rafaela 1 Anoop, Thazhe Veetil 1 Aranda, Carlos Cesar 1 Armstrong, Scott N. 1 Badii, Muricio 1 Badra, Mehdi 1 Bal, Kaushik 1 Bandle, Catherine 1 Benedetti, Irene 1 Biswas, Anup 1 Bobkov, Vladimir E. 1 Bueno, Hamilton P. 1 Cabada, Alberto 1 Campos, Silvina 1 Cao, Bingyang 1 Cardoso, Isolda E. 1 Chakrone, Omar 1 Chang, Xiaojun 1 Chehabi, Hamza 1 Chehabi, Mohammed 1 Choi, Q-Heung 1 Ciani, Simone 1 Cid, José Ángel 1 de Thélin, François 1 Del Pezzo, Leandro M. 1 Dendrinos, Spyridon 1 Derlet, Ann 1 Diaz Diaz, Jesus Ildefonso 1 Durastanti, Riccardo 1 Ercole, Grey 1 Ferreira, Ana Cristina 1 Filippakis, Michael E. 1 Fleckinger, Jacqueline 1 Fragnelli, Genni 1 Gaudiano, Marcos E. 1 Giacomoni, Jacques 1 Grumiau, Christopher 1 Hai, Dang Dinh 1 Hammoudi, Ahmed 1 Heo, Y. R. 1 Hu, Shouchuan 1 Hu, Wenting 1 Húska, Juraj 1 Il’yasov, Yavdat Shavkatovich 1 Iosevich, Alex 1 Iyer, Gautam 1 Ji, Shanming 1 Jung, Tacksun 1 Komorowski, Tomasz 1 Lakmeche, Abdelkader 1 Leadi, Liamidi A. 1 Li, Shunan 1 Li, Yutian 1 Liu, Shuang 1 Lörinczi, József 1 Lou, Yuan 1 Milne, Leandro 1 da Silva Montenegro, Marcelo 1 Mugnai, Dimitri 1 Novikov, Alexei 1 Papalini, Francesca 1 Quaas, Alexander 1 Reichel, Wolfgang 1 Ryzhik, Lenya 1 Saal, Linda V. 1 Sankar, Lakshmi N. ...and 27 more Authors all top 5 Cited in 55 Serials 10 Journal of Mathematical Analysis and Applications 8 Journal of Differential Equations 8 Nonlinear Analysis. Theory, Methods & Applications. Series A: Theory and Methods 5 NoDEA. Nonlinear Differential Equations and Applications 4 Annali di Matematica Pura ed Applicata. Serie Quarta 4 AIMS Mathematics 3 Bulletin of the Australian Mathematical Society 3 Czechoslovak Mathematical Journal 3 Annales de l’Institut Henri Poincaré. Analyse Non Linéaire 3 Discrete and Continuous Dynamical Systems 3 Communications on Pure and Applied Analysis 3 Boundary Value Problems 3 Complex Variables and Elliptic Equations 2 Journal d’Analyse Mathématique 2 Potential Analysis 2 Calculus of Variations and Partial Differential Equations 2 Advanced Nonlinear Studies 2 Journal of Fixed Point Theory and Applications 1 Studia Mathematica 1 Applied Mathematics and Computation 1 Collectanea Mathematica 1 Journal of Functional Analysis 1 Manuscripta Mathematica 1 Mathematische Annalen 1 Mathematics and Computers in Simulation 1 Mathematische Nachrichten 1 Monatshefte für Mathematik 1 Osaka Journal of Mathematics 1 Rendiconti del Circolo Matemàtico di Palermo. Serie II 1 Rendiconti dell’Istituto di Matematica dell’Università di Trieste 1 Rendiconti del Seminario Matematico della Università di Padova 1 Transactions of the American Mathematical Society 1 Forum Mathematicum 1 The Journal of Geometric Analysis 1 Journal of Global Optimization 1 Proceedings of the National Academy of Sciences of the United States of America 1 SIAM Journal on Mathematical Analysis 1 Proceedings of the Indian Academy of Sciences. Mathematical Sciences 1 Electronic Journal of Differential Equations (EJDE) 1 Georgian Mathematical Journal 1 The Journal of Fourier Analysis and Applications 1 Annales Academiae Scientiarum Fennicae. Mathematica 1 Abstract and Applied Analysis 1 Journal of Inequalities and Applications 1 Mathematical Inequalities & Applications 1 Journal of the European Mathematical Society (JEMS) 1 Acta Mathematica Sinica. English Series 1 Communications in Contemporary Mathematics 1 Central European Journal of Mathematics 1 Boletim da Sociedade Paranaense de Matemática. Terceira Série 1 Mediterranean Journal of Mathematics 1 Cubo 1 Journal of Pseudo-Differential Operators and Applications 1 Analysis and Mathematical Physics 1 Advances in Nonlinear Analysis all top 5 Cited in 25 Fields 77 Partial differential equations (35-XX) 16 Harmonic analysis on Euclidean spaces (42-XX) 11 Operator theory (47-XX) 7 Ordinary differential equations (34-XX) 7 Global analysis, analysis on manifolds (58-XX) 3 Integral transforms, operational calculus (44-XX) 3 Functional analysis (46-XX) 3 Differential geometry (53-XX) 2 Topological groups, Lie groups (22-XX) 2 Functions of a complex variable (30-XX) 2 Calculus of variations and optimal control; optimization (49-XX) 2 Probability theory and stochastic processes (60-XX) 1 Nonassociative rings and algebras (17-XX) 1 Real functions (26-XX) 1 Potential theory (31-XX) 1 Dynamical systems and ergodic theory (37-XX) 1 Difference and functional equations (39-XX) 1 Abstract harmonic analysis (43-XX) 1 Integral equations (45-XX) 1 Convex and discrete geometry (52-XX) 1 Classical thermodynamics, heat transfer (80-XX) 1 Quantum theory (81-XX) 1 Statistical mechanics, structure of matter (82-XX) 1 Biology and other natural sciences (92-XX) 1 Systems theory; control (93-XX) Citations by Year