Perhaps you should try some spelling variations:
"central a research firm surveys." » "central a research team surveys.", "central a research firm survey.", "central _ research firm surveys.", "central 2 research firm surveys.", "central tax research firm surveys.", "central s.a research firm surveys."
"central key research firm series." » "central key research team series.", "central led research firm series.", "central does research firm series.", "central _ research firm series.", "central de research firm series.", "central city research firm series.", "centrale des research firm series."

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

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