Perhaps you should try some spelling variations:
"central _ research firm surveys." » "central _ research from surveys.", "central _ research field surveys.", "central _ research final surveys.", "central _ research firm survey."
"central s.a research team series." » "central sla research team series.", "central asia research team series.", "central 2.1 research team series.", "central asian research team series.", "central state research team series.", "central s.a research stem series.", "central s.a research nejm series.", "central s.a research tilsm 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 s.a research team series.") or ("central _ research firm surveys."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("central s.a research team series.") OR ("central _ research firm surveys.")).
• Removing quotes may allow a broader search: (( central s.a research team series. ) or ( central _ research firm surveys. )).
• Adding a wildcard symbol may retrieve word variants: (("central s.a research team series.") or ("central _ research firm surveys."))*.