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 business environment series." » "natural and business environmental services.", "natural and business environmental studies."

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