**Author details**

José Eduardo Ezaquias1,2

1 Cuito Cuanavale University, Angola

2 University of Havana, Angola

\*Address all correspondence to: drezequias@gmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
