| http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_star_formation_in_the_density-wave_model.html |
Chapter
1. Star Formation in the Density-Wave Model
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| http://digfir-published.macmillanusa.com/astro_interactive_exercise/ie_star_formation_in_the_density-wave_model_dlap.xml | DLAP questions | 514138c4b11c0ff21a00000c |