Perhaps you should try some spelling variations:
"improving sector performance studies." » "improving sector performance audits.", "improving sector performance audit.", "improving sector performance standards.", "improve sector performance studies.", "improving eco performance studies.", "improving sewer performance studies."
"importing country performance series." » "importing country performance size.", "important country performance series.", "reporting country performance series.", "exporting country performance series."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("importing country performance series.") or ("improving sector performance studies."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("importing country performance series.") OR ("improving sector performance studies.")).
• Removing quotes may allow a broader search: (( importing country performance series. ) or ( improving sector performance studies. )).
• Adding a wildcard symbol may retrieve word variants: (("importing country performance series.") or ("improving sector performance studies."))*.