Gr 2-4 Significant overlap of information occurs among these books. Common topics include renewable versus nonrenewable resources, kinetic and potential energy, fossil fuels and pollution, global warming, and conservation. Variation occurs in explaining how a specific power source such as wind or solar rays is converted to energy plus the advantages and drawbacks of the process. Beginning report writers might consult an assigned volume to glean basic information, but there is little incentive to read other titles.