Perhaps you should try some spelling variations:
"borrowing country performance series." » "borrowing country performance metrics.", "borrowing country performance reviews.", "borrowing country performance review.", "borrowing countries performance series.", "borrowing costs performance series.", "borrowing cost performance series."
"improving sector performance series." » "improving sector performance metrics.", "improving sector performance reviews.", "improving sector performance review.", "improving export performance series.", "improve sector performance series.", "improving teacher performance series.", "improving weather performance series."

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