Perhaps you should try some spelling variations:
"central tax research tilsm series." » "central tax research team series.", "central tax research tools series.", "central tax research time series.", "central 2 research tilsm series.", "central 2.1 research tilsm series.", "central 2.2 research tilsm series.", "central taxes research tilsm series.", "central bank research tilsm series."
"central e research firm surveys." » "central e research from surveys.", "central e research field surveys.", "central e research final surveys.", "central e research firm survey.", "central use research firm surveys.", "central sme research firm surveys.", "central age research firm surveys.", "central de research firm surveys.", "central _ research firm surveys.", "central 1 research firm surveys."

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

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