Edit Profile (opens in new tab) Nobakhtian, Soghra Co-Author Distance Author ID: nobakhtian.soghra Published as: Nobakhtian, S.; Nobakhtian, Soghra Documents Indexed: 55 Publications since 2000 Co-Authors: 18 Co-Authors with 41 Joint Publications 85 Co-Co-Authors all top 5 Co-Authors 10 single-authored 13 Movahedian, Nooshin 5 Kanzi, Nader 5 Pouryayevali, Mohamad Reza 4 Golestani, Mohammad 3 Hejazi, Mansoureh Alavi 3 Hoseini Monjezi, Najmeh 3 Mashkoorzadeh, Feryal 3 Raeisi Dehkordi, Ahmadreza 2 Monjezi, N. Hoseini 2 Sarabadan, M. 1 Alavi Hejazi, M. 1 Ansari Ardali, A. 1 Ardali, Ali Ansari 1 Castellani, Marco 1 Giuli, Massimiliano 1 Pappalardo, Massimo 1 Shafiei, Narjes 1 Stern, Ronald Jay all top 5 Serials 8 Optimization 7 Journal of Optimization Theory and Applications 6 Numerical Functional Analysis and Optimization 4 Journal of Global Optimization 3 Positivity 3 Optimization Letters 2 Computers & Mathematics with Applications 2 Numerical Algorithms 2 Top 2 Set-Valued and Variational Analysis 1 IMA Journal of Numerical Analysis 1 Journal of Mathematical Analysis and Applications 1 International Journal of Mathematics and Mathematical Sciences 1 Nonlinear Analysis. Theory, Methods & Applications. Series A: Theory and Methods 1 Rendiconti del Circolo Matemàtico di Palermo. Serie II 1 Operations Research Letters 1 Annals of Operations Research 1 European Journal of Operational Research 1 Computational Optimization and Applications 1 Journal of Convex Analysis 1 Mathematical Methods of Operations Research 1 Mathematical Reports 1 4OR 1 Journal of Industrial and Management Optimization 1 Pacific Journal of Optimization Fields 54 Operations research, mathematical programming (90-XX) 35 Calculus of variations and optimal control; optimization (49-XX) 5 Numerical analysis (65-XX) Publications by Year all cited Publications top 5 cited Publications Citations contained in zbMATH Open 48 Publications have been cited 336 times in 206 Documents Cited by ▼ Year ▼ Optimality conditions for nonsmooth semi-infinite multiobjective programming. Zbl 1311.90159 Kanzi, N.; Nobakhtian, S. 31 2014 Optimality conditions for non-smooth semi-infinite programming. Zbl 1195.90088 Kanzi, N.; Nobakhtian, S. 26 2010 Necessary and sufficient conditions for nonsmooth mathematical programs with equilibrium constraints. Zbl 1208.90169 Movahedian, N.; Nobakhtian, S. 21 2010 Convexificators and strong Kuhn-Tucker conditions. Zbl 1252.90073 Golestani, M.; Nobakhtian, Soghra 21 2012 Nonsmooth semi-infinite programming problems with mixed constraints. Zbl 1172.90019 Kanzi, N.; Nobakhtian, S. 18 2009 Optimality conditions for nonsmooth mathematical programs with equilibrium constraints, using convexificators. Zbl 1332.90270 Ardali, A. Ansari; Movahedian, N.; Nobakhtian, S. 16 2016 Optimality criteria for nonsmooth continuous-time problems of multiobjective optimization. Zbl 1194.90088 Nobakhtian, S.; Pouryayevali, M. R. 15 2008 Constraint qualifications for nonsmooth mathematical programs with equilibrium constraints. Zbl 1191.90070 Movahedian, N.; Nobakhtian, S. 12 2009 Nonsmooth multiobjective programming and constraint qualifications. Zbl 1302.90247 Golestani, M.; Nobakhtian, S. 12 2013 Nonsmooth multiobjective programming: strong Kuhn-Tucker conditions. Zbl 1272.90109 Golestani, M.; Nobakhtian, S. 12 2013 Necessary optimality conditions for nonsmooth generalized semi-infinite programming problems. Zbl 1188.90261 Kanzi, N.; Nobakhtian, S. 11 2010 A new infeasible proximal bundle algorithm for nonsmooth nonconvex constrained optimization. Zbl 1425.90084 Hoseini Monjezi, Najmeh; Nobakhtian, S. 11 2019 Optimality and duality for nonsmooth multiobjective fractional programming with mixed constraints. Zbl 1165.90031 Nobakhtian, S. 9 2008 Duality for nonsmooth continuous-time problems of vector optimization. Zbl 1194.90089 Nobakhtian, S.; Pouryayevali, M. R. 9 2008 Infine functions and nonsmooth multiobjective optimization problems. Zbl 1190.90194 Nobakhtian, S. 8 2006 A filter proximal bundle method for nonsmooth nonconvex constrained optimization. Zbl 1465.90073 Hoseini Monjezi, Najmeh; Nobakhtian, S. 8 2021 A Benson type algorithm for nonconvex multiobjective programming problems. Zbl 1372.90085 Nobakhtian, Soghra; Shafiei, Narjes 7 2017 A new trust region method for nonsmooth nonconvex optimization. Zbl 1402.90131 Hoseini, N.; Nobakhtian, S. 7 2018 Optimality criteria and duality in multiobjective programming involving nonsmooth invex functions. Zbl 1133.90394 Nobakhtian, S. 6 2006 Nondifferentiable multiplier rules for optimization problems with equilibrium constraints. Zbl 1229.90142 Movahedian, N.; Nobakhtian, Soghra 6 2009 Multiobjective problems with nonsmooth equality constraints. Zbl 1190.90195 Nobakhtian, S. 5 2009 Universal near-optimal feedbacks. Zbl 1027.49030 Nobakhtian, S.; Stern, R. J. 5 2000 Sufficiency in nonsmooth multiobjective programming involving generalized \(( F, \rho\) )-convexity. Zbl 1278.90362 Nobakhtian, S. 4 2006 Multiobjective problems: enhanced necessary conditions and new constraint qualifications through convexificators. Zbl 1390.49027 Alavi Hejazi, Mansoureh; Movahedian, Nooshin; Nobakhtian, Soghra 4 2018 Nonsmooth multiobjective continuous-time problems with generalized invexity. Zbl 1191.90092 Nobakhtian, S. 4 2009 Optimality conditions for nonconvex constrained optimization problems. Zbl 1472.90100 Mashkoorzadeh, F.; Movahedian, N.; Nobakhtian, S. 4 2019 Optimality conditions for multiobjective fractional programming, via convexificators. Zbl 1449.90333 Hejazi, Mansoureh Alavi; Nobakhtian, Soghra 4 2020 Robustness in nonsmooth nonconvex optimization problems. Zbl 07345591 Mashkoorzadeh, F.; Movahedian, N.; Nobakhtian, S. 4 2021 A proximal bundle-based algorithm for nonsmooth constrained multiobjective optimization problems with inexact data. Zbl 1483.90152 Hoseini Monjezi, N.; Nobakhtian, S. 4 2022 Generalized \((F,\rho )\)-convexity and duality in nonsmooth problems of multiobjective optimization. Zbl 1194.90087 Nobakhtian, S. 3 2008 A proximal bundle algorithm for nonsmooth optimization on Riemannian manifolds. Zbl 1508.65065 Hoseini Monjezi, Najmeh; Nobakhtian, Soghra; Pouryayevali, Mohamad Reza 3 2023 KKT optimality conditions and nonsmooth continuous time optimization problems. Zbl 1232.90335 Nobakhtian, S.; Pouryayevali, M. R. 2 2011 Optimality conditions and duality for nonsmooth fractional continuous-time problems. Zbl 1258.90076 Nobakhtian, S.; Pouryayevali, M. R. 2 2012 Optimality conditions for nonsmooth equilibrium problems via Hadamard directional derivative. Zbl 1387.90239 Ardali, A. Ansari; Movahedian, N.; Nobakhtian, S. 2 2016 Optimality conditions for nonsmooth semidefinite programming via convexificators. Zbl 1342.90124 Golestani, M.; Nobakhtian, S. 2 2015 Nonsmooth multiobjective semi-infinite problems with mixed constraints. Zbl 1474.90491 Kanzi, Nader; Nobakhtian, Soghra 2 2017 An algorithm for generalized constrained multi-source Weber problem with demand substations. Zbl 1457.90090 Nobakhtian, S.; Raeisi Dehkordi, A. 2 2018 Convergence of the proximal bundle algorithm for nonsmooth nonconvex optimization problems. Zbl 1492.90139 Monjezi, N. Hoseini; Nobakhtian, S. 2 2022 An inexact multiple proximal bundle algorithm for nonsmooth nonconvex multiobjective optimization problems. Zbl 1490.90272 Monjezi, N. Hoseini; Nobakhtian, S. 2 2022 On constraint qualifications and sensitivity analysis for general optimization problems via pseudo-Jacobians. Zbl 1402.90205 Hejazi, M. Alavi; Movahedian, N.; Nobakhtian, S. 2 2018 Duality without constraint qualification in nonsmooth optimization. Zbl 1172.90486 Nobakhtian, S. 1 2006 Proximal characterization of Pareto optima. Zbl 1095.90596 Nobakhtian, S. 1 2003 Optimality conditions for isolated local minimum of nonsmooth multiobjective problems. Zbl 1327.90276 Ardali, A. Ansari; Nobakhtian, S. 1 2015 Sensitivity analysis of the value function for nonsmooth optimization problems. Zbl 1409.90194 Alavi Hejazi, M.; Nobakhtian, S. 1 2017 A fast algorithm for the rectilinear distance location problem. Zbl 1406.90072 Nobakhtian, S.; Raeisi Dehkordi, A. 1 2018 Convexificators and boundedness of the Kuhn-Tucker multipliers set. Zbl 1429.90073 Ansari Ardali, A.; Movahedian, N.; Nobakhtian, S. 1 2017 On Abadie constraint qualification for multiobjective optimization problems. Zbl 1404.49013 Alavi Hejazi, Mansoureh; Nobakhtian, Soghra 1 2018 Nonsmooth sparsity constrained optimization problems: optimality conditions. Zbl 1462.90150 Movahedian, N.; Nobakhtian, S.; Sarabadan, M. 1 2019 A proximal bundle algorithm for nonsmooth optimization on Riemannian manifolds. Zbl 1508.65065 Hoseini Monjezi, Najmeh; Nobakhtian, Soghra; Pouryayevali, Mohamad Reza 3 2023 A proximal bundle-based algorithm for nonsmooth constrained multiobjective optimization problems with inexact data. Zbl 1483.90152 Hoseini Monjezi, N.; Nobakhtian, S. 4 2022 Convergence of the proximal bundle algorithm for nonsmooth nonconvex optimization problems. Zbl 1492.90139 Monjezi, N. Hoseini; Nobakhtian, S. 2 2022 An inexact multiple proximal bundle algorithm for nonsmooth nonconvex multiobjective optimization problems. Zbl 1490.90272 Monjezi, N. Hoseini; Nobakhtian, S. 2 2022 A filter proximal bundle method for nonsmooth nonconvex constrained optimization. Zbl 1465.90073 Hoseini Monjezi, Najmeh; Nobakhtian, S. 8 2021 Robustness in nonsmooth nonconvex optimization problems. Zbl 07345591 Mashkoorzadeh, F.; Movahedian, N.; Nobakhtian, S. 4 2021 Optimality conditions for multiobjective fractional programming, via convexificators. Zbl 1449.90333 Hejazi, Mansoureh Alavi; Nobakhtian, Soghra 4 2020 A new infeasible proximal bundle algorithm for nonsmooth nonconvex constrained optimization. Zbl 1425.90084 Hoseini Monjezi, Najmeh; Nobakhtian, S. 11 2019 Optimality conditions for nonconvex constrained optimization problems. Zbl 1472.90100 Mashkoorzadeh, F.; Movahedian, N.; Nobakhtian, S. 4 2019 Nonsmooth sparsity constrained optimization problems: optimality conditions. Zbl 1462.90150 Movahedian, N.; Nobakhtian, S.; Sarabadan, M. 1 2019 A new trust region method for nonsmooth nonconvex optimization. Zbl 1402.90131 Hoseini, N.; Nobakhtian, S. 7 2018 Multiobjective problems: enhanced necessary conditions and new constraint qualifications through convexificators. Zbl 1390.49027 Alavi Hejazi, Mansoureh; Movahedian, Nooshin; Nobakhtian, Soghra 4 2018 An algorithm for generalized constrained multi-source Weber problem with demand substations. Zbl 1457.90090 Nobakhtian, S.; Raeisi Dehkordi, A. 2 2018 On constraint qualifications and sensitivity analysis for general optimization problems via pseudo-Jacobians. Zbl 1402.90205 Hejazi, M. Alavi; Movahedian, N.; Nobakhtian, S. 2 2018 A fast algorithm for the rectilinear distance location problem. Zbl 1406.90072 Nobakhtian, S.; Raeisi Dehkordi, A. 1 2018 On Abadie constraint qualification for multiobjective optimization problems. Zbl 1404.49013 Alavi Hejazi, Mansoureh; Nobakhtian, Soghra 1 2018 A Benson type algorithm for nonconvex multiobjective programming problems. Zbl 1372.90085 Nobakhtian, Soghra; Shafiei, Narjes 7 2017 Nonsmooth multiobjective semi-infinite problems with mixed constraints. Zbl 1474.90491 Kanzi, Nader; Nobakhtian, Soghra 2 2017 Sensitivity analysis of the value function for nonsmooth optimization problems. Zbl 1409.90194 Alavi Hejazi, M.; Nobakhtian, S. 1 2017 Convexificators and boundedness of the Kuhn-Tucker multipliers set. Zbl 1429.90073 Ansari Ardali, A.; Movahedian, N.; Nobakhtian, S. 1 2017 Optimality conditions for nonsmooth mathematical programs with equilibrium constraints, using convexificators. Zbl 1332.90270 Ardali, A. Ansari; Movahedian, N.; Nobakhtian, S. 16 2016 Optimality conditions for nonsmooth equilibrium problems via Hadamard directional derivative. Zbl 1387.90239 Ardali, A. Ansari; Movahedian, N.; Nobakhtian, S. 2 2016 Optimality conditions for nonsmooth semidefinite programming via convexificators. Zbl 1342.90124 Golestani, M.; Nobakhtian, S. 2 2015 Optimality conditions for isolated local minimum of nonsmooth multiobjective problems. Zbl 1327.90276 Ardali, A. Ansari; Nobakhtian, S. 1 2015 Optimality conditions for nonsmooth semi-infinite multiobjective programming. Zbl 1311.90159 Kanzi, N.; Nobakhtian, S. 31 2014 Nonsmooth multiobjective programming and constraint qualifications. Zbl 1302.90247 Golestani, M.; Nobakhtian, S. 12 2013 Nonsmooth multiobjective programming: strong Kuhn-Tucker conditions. Zbl 1272.90109 Golestani, M.; Nobakhtian, S. 12 2013 Convexificators and strong Kuhn-Tucker conditions. Zbl 1252.90073 Golestani, M.; Nobakhtian, Soghra 21 2012 Optimality conditions and duality for nonsmooth fractional continuous-time problems. Zbl 1258.90076 Nobakhtian, S.; Pouryayevali, M. R. 2 2012 KKT optimality conditions and nonsmooth continuous time optimization problems. Zbl 1232.90335 Nobakhtian, S.; Pouryayevali, M. R. 2 2011 Optimality conditions for non-smooth semi-infinite programming. Zbl 1195.90088 Kanzi, N.; Nobakhtian, S. 26 2010 Necessary and sufficient conditions for nonsmooth mathematical programs with equilibrium constraints. Zbl 1208.90169 Movahedian, N.; Nobakhtian, S. 21 2010 Necessary optimality conditions for nonsmooth generalized semi-infinite programming problems. Zbl 1188.90261 Kanzi, N.; Nobakhtian, S. 11 2010 Nonsmooth semi-infinite programming problems with mixed constraints. Zbl 1172.90019 Kanzi, N.; Nobakhtian, S. 18 2009 Constraint qualifications for nonsmooth mathematical programs with equilibrium constraints. Zbl 1191.90070 Movahedian, N.; Nobakhtian, S. 12 2009 Nondifferentiable multiplier rules for optimization problems with equilibrium constraints. Zbl 1229.90142 Movahedian, N.; Nobakhtian, Soghra 6 2009 Multiobjective problems with nonsmooth equality constraints. Zbl 1190.90195 Nobakhtian, S. 5 2009 Nonsmooth multiobjective continuous-time problems with generalized invexity. Zbl 1191.90092 Nobakhtian, S. 4 2009 Optimality criteria for nonsmooth continuous-time problems of multiobjective optimization. Zbl 1194.90088 Nobakhtian, S.; Pouryayevali, M. R. 15 2008 Optimality and duality for nonsmooth multiobjective fractional programming with mixed constraints. Zbl 1165.90031 Nobakhtian, S. 9 2008 Duality for nonsmooth continuous-time problems of vector optimization. Zbl 1194.90089 Nobakhtian, S.; Pouryayevali, M. R. 9 2008 Generalized \((F,\rho )\)-convexity and duality in nonsmooth problems of multiobjective optimization. Zbl 1194.90087 Nobakhtian, S. 3 2008 Infine functions and nonsmooth multiobjective optimization problems. Zbl 1190.90194 Nobakhtian, S. 8 2006 Optimality criteria and duality in multiobjective programming involving nonsmooth invex functions. Zbl 1133.90394 Nobakhtian, S. 6 2006 Sufficiency in nonsmooth multiobjective programming involving generalized \(( F, \rho\) )-convexity. Zbl 1278.90362 Nobakhtian, S. 4 2006 Duality without constraint qualification in nonsmooth optimization. Zbl 1172.90486 Nobakhtian, S. 1 2006 Proximal characterization of Pareto optima. Zbl 1095.90596 Nobakhtian, S. 1 2003 Universal near-optimal feedbacks. Zbl 1027.49030 Nobakhtian, S.; Stern, R. J. 5 2000 all cited Publications top 5 cited Publications all top 5 Cited by 225 Authors 31 Nobakhtian, Soghra 17 Kanzi, Nader 16 Mishra, Shashi Kant 12 Movahedian, Nooshin 9 Tung, Le Thanh 8 Kim, Do Sang 6 Caristi, Giuseppe 6 Hejazi, Mansoureh Alavi 6 Thai Doan Chuong 5 Gadhi, Nazih Abderrazzak 5 Golestani, Mohammad 5 Wu, Hsien-Chung 4 Antczak, Tadeusz 4 Barilla, David 4 Batista Dos Santos, Lucelina 4 Osuna-Gómez, Rafaela 4 Pandey, Yogendra 4 Pham, Thanh Hung 4 Rufián-Lizana, Antonio 4 Ruiz-Garzón, Gabriel 4 Soleimani-damaneh, Majid 4 Su, Tran Van 4 Upadhyay, Balendu Bhooshan 4 Wen, Chingfeng 3 Do Van Luu 3 Hoseini Monjezi, Najmeh 3 Jaiswal, Monika 3 Jović, Aleksandar 3 Le Thi, Hoai An 3 Li, Shengjie 3 Ohda, Mohamed 3 Pang, Liping 3 Phan Quôc Khánh 3 Pouryayevali, Mohamad Reza 3 Sadeghieh, Ali 3 Singh, Yadvendra 3 Sun, Xiangkai 3 Tuyen, Nguyen Van 3 Ulus, Firdevs 3 Yang, Xinmin 2 Aboussoror, Abdelmalek 2 Adly, Samir 2 Arana-Jiménez, Manuel 2 Barton, Paul I. 2 Clarke, Francis H. 2 Dagar, Jyoti 2 de Oliveira, Valeriano Antunes 2 El Idrissi, Mohammed 2 Farajzadeh, Ali P. 2 Feng, Min 2 Ghosh, Arnav 2 Hang, Dinh Dieu 2 Harwood, Stuart M. 2 Hernández-Jiménez, Beatriz 2 Joshi, Bhuwan Chandra 2 Kohli, Bhawna 2 Kumar, Promila 2 Laha, Vivek 2 Lai, K. K. 2 Lalitha, C. S. 2 Lin, Guihua 2 Long, Xianjun 2 Marinković, Boban 2 Mashkoorzadeh, Feryal 2 Maurya, J. K. 2 Mohapatra, Ram Narayan 2 Monjezi, N. Hoseini 2 Raeisi Dehkordi, Ahmadreza 2 Rimpi 2 Rojas-Medar, Marko Antonio 2 Soroush, Hamed 2 Suneja, Surjeet Kaur 2 Tam, Dang Hoang 2 Treanţă, Savin 2 Wu, Qi 2 Zhang, Jin 2 Zhang, Peng 1 Abdulaleem, Najeeb 1 Absil, Pierre-Antoine 1 Ahmad, Izhar 1 Al-Homidan, Suliman S. 1 Alavi Hejazi, M. 1 Ancona, Fabio 1 Ansari Ardali, A. 1 Anshika 1 Ararat, Çağın 1 Ardali, Ali Ansari 1 Banerjee, Jonaki 1 Beni-Asad, M. 1 Bento, Glaydston de Carvalho 1 Bhatia, Meetu 1 Bisht, Jaya 1 Viero Brandão, Adilson José 1 Bressan, Alberto 1 Castellani, Marco 1 Chalco-Cano, Yurilev 1 Chen, Jiawei 1 Chen, Shenghong 1 Chen, Zhangyou 1 Chen, Zhe ...and 125 more Authors all top 5 Cited in 64 Serials 20 Optimization 16 Journal of Optimization Theory and Applications 15 Journal of Global Optimization 12 Numerical Functional Analysis and Optimization 9 Optimization Letters 7 Positivity 7 Journal of Inequalities and Applications 7 Journal of Industrial and Management Optimization 6 Annals of Operations Research 4 Nonlinear Analysis. Theory, Methods & Applications. Series A: Theory and Methods 4 European Journal of Operational Research 4 SIAM Journal on Optimization 4 Computational and Applied Mathematics 4 Top 4 RAIRO. Operations Research 4 Journal of Mathematical Extension 3 Numerical Algorithms 3 YUJOR. Yugoslav Journal of Operations Research 3 Journal of Systems Science and Complexity 3 Iranian Journal of Science and Technology. Transaction A: Science 3 Journal of Applied Mathematics and Computing 3 Set-Valued and Variational Analysis 3 Journal of the Operations Research Society of China 3 Journal of Nonlinear and Variational Analysis 2 Computers & Mathematics with Applications 2 Journal of Mathematical Analysis and Applications 2 Rendiconti del Circolo Matemàtico di Palermo. Serie II 2 Bulletin of the Iranian Mathematical Society 2 Computational Optimization and Applications 2 Optimization Methods & Software 2 Decisions in Economics and Finance 2 Bulletin of the Malaysian Mathematical Sciences Society. Second Series 2 Bulletin of the Brazilian Mathematical Society. New Series 2 Iranian Journal of Fuzzy Systems 2 Minimax Theory and its Applications 1 Applicable Analysis 1 Acta Mathematica Vietnamica 1 Applied Mathematics and Computation 1 Applied Mathematics and Optimization 1 Journal of Computational and Applied Mathematics 1 Opsearch 1 Operations Research Letters 1 Annales de l’Institut Henri Poincaré. Analyse Non Linéaire 1 Computers & Operations Research 1 Asia-Pacific Journal of Operational Research 1 Journal of Scientific Computing 1 Mathematical Programming. Series A. Series B 1 Applicationes Mathematicae 1 Turkish Journal of Mathematics 1 Filomat 1 European Journal of Control 1 European Series in Applied and Industrial Mathematics (ESAIM): Control, Optimization and Calculus of Variations 1 Abstract and Applied Analysis 1 Mathematical Methods of Operations Research 1 Differential Equations 1 Acta Mathematica Scientia. Series B. (English Edition) 1 Computational Management Science 1 International Journal of Numerical Analysis and Modeling 1 Mathematics and Financial Economics 1 S\(\vec{\text{e}}\)MA Journal 1 Journal of Applied Analysis and Computation 1 Mathematical Sciences 1 Computational Methods for Differential Equations 1 AIMS Mathematics all top 5 Cited in 15 Fields 197 Operations research, mathematical programming (90-XX) 91 Calculus of variations and optimal control; optimization (49-XX) 21 Numerical analysis (65-XX) 8 Real functions (26-XX) 7 Functional analysis (46-XX) 6 Operator theory (47-XX) 4 Game theory, economics, finance, and other social and behavioral sciences (91-XX) 3 Systems theory; control (93-XX) 2 Dynamical systems and ergodic theory (37-XX) 1 Partial differential equations (35-XX) 1 Approximations and expansions (41-XX) 1 Differential geometry (53-XX) 1 Global analysis, analysis on manifolds (58-XX) 1 Mechanics of deformable solids (74-XX) 1 Optics, electromagnetic theory (78-XX) Citations by Year