Links
[1] https://www.hootsgo.org/?q=node/6395
[2] http://en.wikipedia.org/wiki/Electrochemical_cell
[3] http://simple.wikipedia.org/wiki/Electrical_cell
[4] http://resources.schoolscience.co.uk/BritishEnergy/11-14/circh1pg2.html
[5] http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/electrochem.html