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 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.", "central s.2 research team 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 a research firm survey."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("central s.a research team series.") OR ("central a research firm survey."))*.
• Removing quotes may allow a broader search: (( central s.a research team series. ) or ( central a research firm survey. ))*.