<http://www.w3.org/1999/02/22-rdf-syntax-ns#first>
<http://ichef.bbci.co.uk/news/ws/560/amz/worldservice/live/assets/images/2013/03/07/130307161558_sach_hoc_van_304x171_tuoitre.vn.jpg>
<http://bbcvietnamese.com/vietnamese/vietnam/2013/03/130312_sach_tre_em_luoi_bo.shtml>