Perhaps you should try some spelling variations:
"central a research firm survey." » "central a research from survey.", "central a research field survey.", "central a research final survey.", "central 2 research firm survey.", "central la research firm survey.", "central _ research firm survey.", "central 1 research firm survey."
"central s.a research areas series." » "central sla research areas series.", "central asia research areas series.", "central 2.1 research areas series.", "central s.a research areas services.", "central s.a research ideas series.", "central s.a research seas series.", "central asian research areas series.", "central state research areas series.", "central s.2 research areas series."

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: (("central s.a research areas series.") or ("central a research firm survey."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("central s.a research areas series.") OR ("central a research firm survey.")).
• Removing quotes may allow a broader search: (( central s.a research areas series. ) or ( central a research firm survey. )).
• Adding a wildcard symbol may retrieve word variants: (("central s.a research areas series.") or ("central a research firm survey."))*.