Perhaps you should try some spelling variations:
"Natural and gas environmental resource." » "Natural and gas environmental resources.", "Natural and gas environmental research.", "Natural and gas environmental pressures.", "Natural and gases environmental resource.", "Natural and dams environmental resource.", "Natural and its environmental resource."
"natural and built environment series." » "natural and built environmental services.", "natural and built environmental studies."

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("natural and built environment series.") or ("Natural and gas environmental resource."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("natural and built environment series.") OR ("Natural and gas environmental resource.")).
• Removing quotes may allow a broader search: (( natural and built environment series. ) or ( Natural and gas environmental resource. )).
• Adding a wildcard symbol may retrieve word variants: (("natural and built environment series.") or ("Natural and gas environmental resource."))*.