This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms
of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 (CC BY-NC-ND) License which permits use,
distribution and reproduction, provided that the original work is properly cited, the use is non-commercial and no
modifications or adaptations are made.
Excepto si se señala otra cosa, la licencia del ítem se describe como This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 (CC BY-NC-ND) License which permits use, distribution and reproduction, provided that the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.