{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,26]],"date-time":"2025-12-26T01:19:07Z","timestamp":1766711947718,"version":"build-2065373602"},"reference-count":60,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2019,2,7]],"date-time":"2019-02-07T00:00:00Z","timestamp":1549497600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["MTM2015-63978-P","TIN2016-76259-P","TEC2017-86722-C4-2-R"],"award-info":[{"award-number":["MTM2015-63978-P","TIN2016-76259-P","TEC2017-86722-C4-2-R"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Gobierno de Extremadura","award":["GR15106","IB16002"],"award-info":[{"award-number":["GR15106","IB16002"]}]},{"DOI":"10.13039\/501100002848","name":"Comisi\u00f3n Nacional de Investigaci\u00f3n Cient\u00edfica y Tecnol\u00f3gica","doi-asserted-by":"publisher","award":["1171243","1160455"],"award-info":[{"award-number":["1171243","1160455"]}],"id":[{"id":"10.13039\/501100002848","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>During the last decade, Wireless sensor networks (WSNs) have attracted interest due to the excellent monitoring capabilities offered. However, WSNs present shortcomings, such as energy cost and reliability, which hinder real-world applications. As a solution, Relay Node (RN) deployment strategies could help to improve WSNs. This fact is known as the Relay Node Placement Problem (RNPP), which is an NP-hard optimization problem. This paper proposes to address two Multi-Objective (MO) formulations of the RNPP. The first one optimizes average energy cost and average sensitivity area. The second one optimizes the two previous objectives and network reliability. The authors propose to solve the two problems through a wide range of MO metaheuristics from the three main groups in the field: evolutionary algorithms, swarm intelligence algorithms, and trajectory algorithms. These algorithms are the Non-dominated Sorting Genetic Algorithm II (NSGA-II), Strength Pareto Evolutionary Algorithm 2 (SPEA2), Multi-Objective Evolutionary Algorithm based on Decomposition (MOEA\/D), Multi-Objective Artificial Bee Colony (MO-ABC), Multi-Objective Firefly Algorithm (MO-FA), Multi-Objective Gravitational Search Algorithm (MO-GSA), and Multi-Objective Variable Neighbourhood Search Algorithm (MO-VNS). The results obtained are statistically analysed to determine if there is a robust metaheuristic to be recommended for solving the RNPP independently of the number of objectives.<\/jats:p>","DOI":"10.3390\/s19030677","type":"journal-article","created":{"date-parts":[[2019,2,7]],"date-time":"2019-02-07T11:50:33Z","timestamp":1549540233000},"page":"677","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Toward a Robust Multi-Objective Metaheuristic for Solving the Relay Node Placement Problem in Wireless Sensor Networks"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1083-5015","authenticated-orcid":false,"given":"Jos\u00e9 M.","family":"Lanza-Guti\u00e9rrez","sequence":"first","affiliation":[{"name":"Escuela T\u00e9cnica Superior de Ingenieros Industriales, Centro de Electr\u00f3nica Industrial, Universidad Polit\u00e9cnica de Madrid, 28006 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4750-2900","authenticated-orcid":false,"given":"Nuria","family":"Caball\u00e9","sequence":"additional","affiliation":[{"name":"Facultad de Farmacia, Campus Montepr\u00edncipe, Universidad CEU San Pablo, 28668 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0441-9402","authenticated-orcid":false,"given":"Juan A.","family":"G\u00f3mez-Pulido","sequence":"additional","affiliation":[{"name":"Escuela Pol\u00edt\u00e9cnica, Universidad de Extremadura, 10003 C\u00e1ceres, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5500-0188","authenticated-orcid":false,"given":"Broderick","family":"Crawford","sequence":"additional","affiliation":[{"name":"Escuela de Ingenier\u00eda Inform\u00e1tica, Pontificia Universidad Cat\u00f3lica de Valpara\u00edso, 2362807 Valpara\u00edso, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5755-6929","authenticated-orcid":false,"given":"Ricardo","family":"Soto","sequence":"additional","affiliation":[{"name":"Escuela de Ingenier\u00eda Inform\u00e1tica, Pontificia Universidad Cat\u00f3lica de Valpara\u00edso, 2362807 Valpara\u00edso, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,2,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2392","DOI":"10.1109\/TIE.2016.2619319","article-title":"Packet size optimization in wireless sensor networks for smart grid applications","volume":"64","author":"Kurt","year":"2017","journal-title":"IEEE Trans. Ind. Electron."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1016\/j.comcom.2015.09.006","article-title":"A survey on wireless sensor networks for smart grid","volume":"71","author":"Fadel","year":"2015","journal-title":"Comput. Commun."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2963","DOI":"10.1109\/JSEN.2014.2383996","article-title":"A low cost, highly scalable wireless sensor network solution to achieve smart LED light control for green buildings","volume":"15","author":"Magno","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1109\/MCOM.2002.1024422","article-title":"A survey on sensor networks","volume":"40","author":"Akyildiz","year":"2002","journal-title":"IEEE Commun. Mag."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"2066","DOI":"10.1109\/JSYST.2017.2673759","article-title":"QERP: Quality-of-Service (QoS) Aware Evolutionary Routing Protocol for Underwater Wireless Sensor Networks","volume":"12","author":"Faheem","year":"2017","journal-title":"IEEE Syst. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"104","DOI":"10.1016\/j.comnet.2014.03.027","article-title":"Energy efficiency in wireless sensor networks: A top-down survey","volume":"67","author":"Rault","year":"2014","journal-title":"Comput. Netw."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2579","DOI":"10.1109\/TWC.2005.853969","article-title":"On energy provisioning and relay node placement for wireless sensor networks","volume":"4","author":"Hou","year":"2005","journal-title":"IEEE Trans. Wireless Commun."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1109\/TMC.2003.1233530","article-title":"Strong minimum energy topology in wireless sensor networks: NP-completeness and heuristics","volume":"2","author":"Cheng","year":"2003","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"609","DOI":"10.1109\/TNET.2004.833122","article-title":"Maximum lifetime routing in wireless sensor networks","volume":"12","author":"Chang","year":"2004","journal-title":"IEEE\/ACM Trans. Netw."},{"key":"ref_10","unstructured":"Vazirani, V.V. (2001). Approximation Algorithms, Springer."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1016\/j.ic.2017.06.001","article-title":"Exact algorithms for maximum independent set","volume":"255","author":"Xiao","year":"2017","journal-title":"Inf. Comput."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Deb, K. (2014). Multi-objective optimization. Search Methodologies, Springer.","DOI":"10.1007\/978-1-4614-6940-7_15"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1145\/937503.937505","article-title":"Metaheuristics in combinatorial optimization: Overview and conceptual comparison","volume":"35","author":"Blum","year":"2003","journal-title":"ACM Comput. Surv."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1109\/4235.996017","article-title":"A Fast Elitist Multi-Objective Genetic Algorithm: NSGA-II","volume":"6","author":"Deb","year":"2000","journal-title":"IEEE Trans. Evolut. Comput."},{"key":"ref_15","unstructured":"Zitzler, E., Laumanns, M., and Thiele, L. (2001). SPEA2: Improving the Strength Pareto Evolutionary Algorithm, Computer Engineering and Networks Laboratory (TIK), ETH Zurich. Technical Report."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"712","DOI":"10.1109\/TEVC.2007.892759","article-title":"MOEA\/D: A Multiobjective Evolutionary Algorithm Based on Decomposition","volume":"11","author":"Zhang","year":"2007","journal-title":"IEEE Trans. Evolut. Comput."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"459","DOI":"10.1007\/s10898-007-9149-x","article-title":"A powerful and efficient algorithm for numerical function optimization: Artificial bee colony (ABC) algorithm","volume":"39","author":"Karaboga","year":"2007","journal-title":"J. Glob. Optim."},{"key":"ref_18","first-page":"169","article-title":"Firefly Algorithms for Multimodal Optimization","volume":"Volume 5792","author":"Yang","year":"2009","journal-title":"Stochastic Algorithms: Foundations and Applications"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2232","DOI":"10.1016\/j.ins.2009.03.004","article-title":"GSA: A Gravitational Search Algorithm","volume":"179","author":"Rashedi","year":"2009","journal-title":"Inf. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1097","DOI":"10.1016\/S0305-0548(97)00031-2","article-title":"Variable neighborhood search","volume":"24","author":"Hansen","year":"1997","journal-title":"Comput. Oper. Res."},{"key":"ref_21","unstructured":"Lanza-Gutierrez, J.M., Gomez-Pulido, J.A., Vega-Rodriguez, M.A., and Sanchez-Perez, J.M. (2019, February 05). Instance Sets for Optimization in Wireless Sensor Networks. Available online: http:\/\/arco.unex.es\/wsnopt."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.comcom.2004.12.032","article-title":"Relay node placement in large scale wireless sensor networks","volume":"29","author":"Tang","year":"2006","journal-title":"Comput. Commun."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2444","DOI":"10.1109\/TWC.2007.05357","article-title":"Device Placement for Heterogeneous Wireless Sensor Networks: Minimum Cost with Lifetime Constraints","volume":"6","author":"Wang","year":"2007","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"134","DOI":"10.1109\/TC.2007.250629","article-title":"Relay Node Placement in Wireless Sensor Networks","volume":"56","author":"Lloyd","year":"2007","journal-title":"IEEE Trans. Comput."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"643","DOI":"10.1109\/TMC.2009.161","article-title":"Fault-Tolerant Relay Node Placement in Heterogeneous Wireless Sensor Networks","volume":"9","author":"Han","year":"2010","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1109\/TMC.2009.105","article-title":"Relay Node Deployment Strategies in Heterogeneous Wireless Sensor Networks","volume":"9","author":"Xu","year":"2010","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Misra, S., Majd, N., and Huang, H. (2011, January 17\u201322). Constrained Relay Node Placement in Energy Harvesting Wireless Sensor Networks. Proceedings of 2011 IEEE Eighth International Conference on Mobile Ad-Hoc and Sensor Systems, Valencia, Spain.","DOI":"10.1109\/MASS.2011.137"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"220","DOI":"10.1016\/j.ejor.2013.08.031","article-title":"Optimal relay node placement in delay constrained wireless sensor network design","volume":"233","author":"Nigam","year":"2014","journal-title":"Eur. J. Oper. Res."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2933","DOI":"10.1109\/TC.2013.171","article-title":"Approximation algorithms for constrained relay node placement in energy harvesting wireless sensor networks","volume":"63","author":"Misra","year":"2014","journal-title":"IEEE Trans. Comput."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1109\/JSEN.2015.2456931","article-title":"A connectivity-aware approximation algorithm for relay node placement in wireless sensor networks","volume":"16","author":"Ma","year":"2016","journal-title":"IEEE Sens. J."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1109\/TSUSC.2017.2666844","article-title":"Energy-aware constrained relay node deployment for sustainable wireless sensor networks","volume":"2","author":"Djenouri","year":"2017","journal-title":"IEEE Trans. Sustain. Comput."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"371","DOI":"10.1016\/j.compeleceng.2015.09.014","article-title":"Relay node placement to heal partitioned wireless sensor networks","volume":"48","author":"Ranga","year":"2015","journal-title":"Comput. Electr. Eng."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"667","DOI":"10.1109\/JSEN.2014.2351405","article-title":"An alternative node deployment scheme for WSNs","volume":"15","author":"Izadi","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"197","DOI":"10.1007\/s10732-014-9256-z","article-title":"Planning the deployment of multiple sinks and relays in wireless sensor networks","volume":"21","author":"Sitanayah","year":"2015","journal-title":"J. Heuristics"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2205","DOI":"10.1109\/TWC.2017.2658598","article-title":"Optimal placement of relay nodes over limited positions in wireless sensor networks","volume":"16","author":"Bagaa","year":"2017","journal-title":"IEEE Trans. Wirel. Commun."},{"key":"ref_36","unstructured":"Zhao, C., and Chen, P. (2007, January 25\u201328). Particle swarm optimization for optimal deployment of relay nodes in hybrid sensor networks. Proceedings of the 2007 IEEE Congress on Evolutionary Computation, Singapore."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Perez, A., Labrador, M., and Wightman, P. (2011, January 28\u201331). A multiobjective approach to the relay placement problem in WSNs. Proceedings of the IEEE WCNC, Cancun, Quintana Roo, Mexico.","DOI":"10.1109\/WCNC.2011.5779179"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"114","DOI":"10.1002\/dac.1336","article-title":"An optimal energy-efficient clustering method in wireless sensor networks using multi-objective genetic algorithm","volume":"26","author":"Peiravi","year":"2013","journal-title":"Int. J. Commun. Syst."},{"key":"ref_39","unstructured":"Gupta, S.K., Kuila, P., and Jana, P.K. Genetic algorithm for k-connected relay node placement in wireless sensor networks. Proceedings of the Second International Conference on Computer and Communication Technologies."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1016\/j.jnca.2015.09.013","article-title":"Optimal placement of relay nodes in wireless sensor network using artificial bee colony algorithm","volume":"64","author":"Hashim","year":"2016","journal-title":"J. Netw. Comput. Appl."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"George, J., and Sharma, R.M. (2016, January 21\u201323). Relay node placement in wireless sensor networks using modified genetic algorithm. Proceedings of the 2016 2nd International Conference on Applied and Theoretical Computing and Communication Technology (iCATccT), Bangalore, India.","DOI":"10.1109\/ICATCCT.2016.7912061"},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Yu, W., Li, X., Yang, H., and Huang, B. (2017). A Multi-Objective Metaheuristics Study on Solving Constrained Relay Node Deployment Problem in WSNS. Intell. Automa. Soft Comput.","DOI":"10.1080\/10798587.2017.1294873"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"263","DOI":"10.1016\/j.csi.2011.03.004","article-title":"A review of wireless sensors and networks: Applications in agriculture","volume":"36","author":"Abbasi","year":"2014","journal-title":"Comput. Stand. Interfaces"},{"key":"ref_44","first-page":"1","article-title":"Intelligent Relay Node Placement in Heterogeneous Wireless Sensor Networks for Energy Efficiency","volume":"29","year":"2014","journal-title":"Int. J. Robot. Autom."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Lanza-Gutierrez, J.M., and Gomez-Pulido, J.A. (2015). A gravitational search algorithm for solving the relay node placement problem in wireless sensor networks. Int. J. Commun. Syst.","DOI":"10.1002\/dac.2957"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Lanza-Gutierrez, J.M., and Gomez-Pulido, J.A. (2015). Studying the multiobjective variable neighbourhood search algorithm when solving the relay node placement problem in Wireless Sensor Networks. Soft Comput.","DOI":"10.1002\/dac.2957"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"675","DOI":"10.1016\/j.asoc.2015.01.051","article-title":"Assuming multiobjective metaheuristics to solve a three-objective optimisation problem for Relay Node deployment in Wireless Sensor Networks","volume":"30","year":"2015","journal-title":"Appl. Soft Comput."},{"key":"ref_48","unstructured":"Cormen, T.H., Leiserson, C.E., Rivest, R.L., and Stein, C. (2009). Introduction to Algorithms(Third Edition), The MIT Press."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Konstantinidis, A., Yang, K., and Zhang, Q. (December, January 30). An Evolutionary Algorithm to a Multi-Objective Deployment and Power Assignment Problem in Wireless Sensor Networks. Proceedings of the IEEE GLOBECOM 2008 IEEE Global Telecommunications Conference, New Orleans, LO, USA.","DOI":"10.1109\/GLOCOM.2008.ECP.98"},{"key":"ref_50","unstructured":"Fewell, M. (2006). Area of Common Overlap of Three Circles, Defence Science and Technology Organization. Technical Report; Maritime Operations Division."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"545","DOI":"10.1109\/JSEN.2010.2048897","article-title":"A hybrid multiobjective evolutionary approach for improving the performance of wireless sensor networks","volume":"11","author":"Martins","year":"2011","journal-title":"IEEE Sens. J."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1093","DOI":"10.1109\/TSMCC.2012.2196996","article-title":"An evolutionary multiobjective sleep-scheduling scheme for differentiated coverage in wireless sensor networks","volume":"42","author":"Sengupta","year":"2012","journal-title":"IEEE Trans. Syst. Man Cybern. Part C"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1016\/j.engappai.2012.05.018","article-title":"Multi-objective node deployment in WSNs: In search of an optimal trade-off among coverage, lifetime, energy consumption, and connectivity","volume":"26","author":"Sengupta","year":"2013","journal-title":"Eng. Appl. Artif. Intell."},{"key":"ref_54","unstructured":"Deb, B., Bhatnagar, S., and Nath, B. (2003, January 20\u201324). Reliable Information Forwarding Using Multiple Paths in Sensor Networks. Proceedings of the 28th Annual IEEE International Conference on Local Computer Networks, Germany, Germany."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1002\/net.3230040204","article-title":"Disjoint paths in a network","volume":"4","author":"Suurballe","year":"1974","journal-title":"Networks"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"537","DOI":"10.1016\/j.adhoc.2008.06.003","article-title":"Energy conservation in wireless sensor networks: A survey","volume":"7","author":"Anastasi","year":"2009","journal-title":"Ad Hoc Netw."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1016\/j.jnca.2011.11.016","article-title":"A survey on coverage and connectivity issues in wireless sensor networks","volume":"35","author":"Zhu","year":"2012","journal-title":"J. Netw. Comput. Appl."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"1243","DOI":"10.1109\/TSMCC.2012.2205680","article-title":"Wireless Sensor Network Reliability and Security in Factory Automation: A Survey","volume":"42","author":"Islam","year":"2012","journal-title":"IEEE Trans. Syst. Man Cybern. Part C Appl. Rev."},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/j.ins.2014.08.004","article-title":"A multiobjective evolutionary algorithm based on decomposition with normal boundary intersection for traffic grooming in optical networks","volume":"289","author":"Zhang","year":"2014","journal-title":"Inf. Sci."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/j.comcom.2010.08.011","article-title":"Multi-objective K-connected Deployment and Power Assignment in WSNs using a problem-specific constrained evolutionary algorithm based on decomposition","volume":"34","author":"Konstantinidis","year":"2011","journal-title":"Comput. Commun."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/3\/677\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:31:32Z","timestamp":1760185892000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/3\/677"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,2,7]]},"references-count":60,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2019,2]]}},"alternative-id":["s19030677"],"URL":"https:\/\/doi.org\/10.3390\/s19030677","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2019,2,7]]}}}