1. Universidad Nacional de Colombia-Manizales, Department of Mathematics and Statistics, FIZMAKO Research Group, Manizales, Colombia
2. Universidad Nacional de Colombia-Manizales-Caldas, Department of Mathematics and Statistics, Manizales, Caldas, Colombia
3. Universidad de Caldas, Department of Mathematics and Statistics, Caldas, Manizales, Colombia
4. Universidad Nacional de Colombia, Department of Mathematics and Statistics, Manizales, Colombia