Perhaps you should try some spelling variations:
"central basic research a series." » "central based research a series.", "central asia research a series.", "central bajio research a series.", "neutral basic research a series."
"central key research firm surveys." » "central key research from surveys.", "central key research field surveys.", "central key research final surveys.", "central 1.1 research firm surveys.", "central 1.2 research firm surveys.", "central 1 research firm surveys.", "central key research firm survey.", "central de research firm surveys.", "central city research firm surveys.", "central body research firm surveys."

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