URL	Title	Id
http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_the_rotation_of_our_galaxy.html	Chapter 1. The Rotation of Our Galaxy	51413892b11c0ff21a000007
http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_the_rotation_of_our_galaxy_dlap.xml	DLAP questions	51413892b11c0ff21a000007