String Explorer (red book)

http://www.youtube.com/watchv=Z_Mqji7c2Ng&w=380&h=240

http://www.youtube.com/watchv=4gLNzfj8KE0&w=380&h=240

http://www.youtube.com/watchv=HJIrpguY5k0&w=380&h=240

http://www.youtube.com/watchv=61cyblwxXA4&w=380&h=240