1.http://www.ratchanee.thport.com/E-learning/structure_cell.html
2.http://www.thaigoodview.com/node/17529
4.http://www.trueplookpanya.com/true/knowledge_detail.php?mul_content_id=1272
5.http://www.ipecp.ac.th/ipecp/cgi-binn/BP1/Program/chapter3/p5.html