<https://www.careeste.ro/care-este-legatura-dintre-unghiul-de-incidenta-si-unghiul-de-refractie/#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.careeste.ro/care-este-legatura-dintre-unghiul-de-incidenta-si-unghiul-de-refractie/>