Perhaps you should try some spelling variations:
"renewable energy resources" » "renewable energy sources", "renewable energy resource"
"renewable energy resource" » "renewable energy source"
"renewable energy sources" » "renewable energy source"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((((("renewable energy sources") OR ("renewable energy resources"))) OR ("renewable energy resources"))) OR ("renewable energy resource")).
• Removing quotes may allow a broader search: (((((( renewable energy sources ) or ( renewable energy resources ))) or ( renewable energy resources ))) or ( renewable energy resource )).
• Adding a wildcard symbol may retrieve word variants: (((((("renewable energy sources") or ("renewable energy resources"))) or ("renewable energy resources"))) or ("renewable energy resource"))*.