URL	Title	Id
http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_internal_structures_of_mercury_and_earth.html	Chapter 1. The Internal Structures of Mercury and Earth	513aaab1b11c0f1e5b000001
http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_internal_structures_of_mercury_and_earth_dlap.xml	DLAP questions	513aaab1b11c0f1e5b000001