Sources
- http://www.hp.com/hpinfo/newsroom/press_kits/environment/images/plant_conveyor_belt.png
- http://www.engineershandbook.com/Tables/frictioncoefficients.htm
- http://www.fao.org/docrep/S4314E/s4314e3o.gif
- http://www.youtube.com/watch?v=BsyDTyweenc
- http://www.youtube.com/watch?feature=endscreen&NR=1&v=9XhgaCrwK_U
- http://www.youtube.com/watch?v=w10UqrBehK0
- http://EzineArticles.com/353910