1. Dept. of Mathematics, Univ. of Castilla–La Mancha, Ciudad Real, Spain (corresponding author).
2. Dept. of Applied Mathematics and Computational Sciences, Univ. of Cantabria, Santander, Spain.
3. Dept. of Mathematics, Univ. of Castilla–La Mancha, Ciudad Real, Spain.
4. Dept. of Civil Engineering, Univ. of Castilla–La Mancha, Ciudad Real, Spain.