1. http://202.44.68.33/library/exam/intro/class4.htm
2. http://202.44.68.33/library/studentshow/st2546/4-7/no08/test01/index.html
3. http://school.obec.go.th/mclschool/6.2.2/L2.htm
4. http://www.montfort.ac.th/mcs/dept/science/scienceteachers/nittaya/ex/biochem-test.html
5. http://www.sc.psu.ac.th/department/bio/st/data/bascichem.pdf