http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_part1_faces_of_the_sun.html
Chapter
1. Faces of the Sun
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http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_part1_faces_of_the_sun_dlap.xmlDLAP questions513dc738b11c0f0b69000002