http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_the_geometry_of_the_universe.html |
Chapter
1. The Geometry of the Universe
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http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_the_geometry_of_the_universe_dlap.xml | DLAP questions | 51413996b11c0f181b00000f |