Perhaps you should try some spelling variations:
"central africa's research firm survey." » "central african research firm survey.", "central africa research firm survey.", "central americans research firm survey.", "central america's research firm survey.", "central asia's research firm survey.", "central africa's research from survey.", "central africa's research field survey.", "central africa's research final survey."
"central basic research team series." » "central based research team series.", "central asia research team series.", "central bajio research team series.", "neutral basic research team series.", "central basic research stem series.", "central basic research nejm series.", "central basic 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 basic research team series.") or ("central africa's research firm survey."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("central basic research team series.") OR ("central africa's research firm survey."))*.
• Removing quotes may allow a broader search: (( central basic research team series. ) or ( central africa's research firm survey. ))*.