This work has received financial support of the Call 2015 Grants for Ph.D. contracts for training of doctors of the Ministry of Economy and Competitiveness, cofinanced by the European Social Fund (Ref. BES-2015-074958 ). We acknowledge support from MTM2014-55966-P project, Ministry of Economy and Competitiveness, Spain , and MTM2017-89422-P project, Ministry of Economy, Industry and Competitiveness, Spain , State Research Agency, Spain , and Regional Development Fund , UE. We also acknowledge the financial support provided by the SiDOR (Statistical Inference, Decision and Operations Research), Spain group through the grant Competitive Reference Group, 2016–2019 ( ED431C 2016/040 ), funded by the “ Consellería de Cultura, Educación e Ordenación Universitaria. Xunta de Galicia, Spain ”. Support from the “ Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016-2019)” and the European Union (European Regional Development Fund - ERDF) , is gratefully acknowledged. To finish, the first author would like to thank the University of Vigo, Spain , and its Escola Internacional de Doutoramento (EIDO) by the financial support provided through mobility doctorate grants. Appendix A