<https://blogkienthuc.net/y-nghia-cac-con-so-tu-00-den-99-trong-lo-de-chinh-xac>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://blogkienthuc.net/y-nghia-cac-con-so-tu-00-den-99-trong-lo-de-chinh-xac>