อ้างอิง

1.http://www.thaimeboard.com/faq/qa-id14.html
2.http://portal.edu.chula.ac.th/peng/blog/view.php?Bid=1277613762810293
3.https://sites.google.com/site/tirmaspannil/kar-subkhn-khxmul/4-websit-search-engine-thi-di-rab-khwam-niym
4.http://blog.seo.co.th/%E0%B8%9B%E0%B8%A3%E0%B8%B0%E0%B9%80%E0%B8%A0%E0%B8%97%E0%B8%82%E0%B8%AD%E0%B8%87-search-engine