<https://secure.gravatar.com/avatar/be2e544502ceca546154f9a4323c295f?s=96&amp;d=blank&amp;r=g>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://cursosonlineweb.com/propiedades-de-los-logaritmos.html>