[1] Univ Vigo, Dept Estat & Invest Operat, Vigo 36310, Spain
[2] Univ A Coruna, Dept Matemat, La Coruna, Spain
[3] Univ Miguel Hernandez Elche, Ctr Invest Operat, Elche, Spain
[4] Univ Vigo, Fac Ciencias Empresariais & Turismo, Dept Estat & Invest Operat, Orense, Spain