1. Laboratory of Mathematics, Sidi-Bel-Abbès University, 89, 22000 Sidi-Bel-Abbès, Algeria
2. Departamento de Estatística, Análisis Matemático e Optimización, Instituto de Matemáticas, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
3. Department of Mathematics and Informatics, The African University Ahmed Draia of Adrar, Adrar, Algeria