Perhaps you should try some spelling variations:
"central action research firm series." » "central national research firm series.", "central station research firm series.", "central asian research firm series.", "central region research firm series.", "central action research team series."
"central peace research firm surveys." » "central science research firm surveys.", "central peace research team surveys.", "central rate research firm surveys.", "central peace research firm survey."

You may be able to get more results by adjusting your search query.

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