http://www.microsoft.com/learning/elearning.mspx

http://psych.hanover.edu/Krantz/tutor.html#Sensation%20and%20Perception

http://facultyweb.cortland.edu/~andersmd/edpsy.html

http://coe.sdsu.edu/eet/articles/realtimefbk/index.htm

http://psych.athabascau.ca/html/prtut/reinpair.htm

http://www.dushkin.com/connectext/econ/

http://www.sparknotes.com/economics/

http://www.usm.my