Exercise1: http://www.youtube.com/watch?v=KIPwOwm7IcQ
Exercise 2: http://www.youtube.com/watch?v=JnfBXjWm7hc
Exercise 3: http://www.youtube.com/watch?v=Q5WT2vweFRY&feature=related
Exercise 4: http://www.youtube.com/watch?v=-8c50Z0J8ts
Units 4- 7- 9 are not included in the final
