Perhaps you should try some spelling variations:
"central a research program synthesis." » "central a research programs synthesis.", "central a research project synthesis.", "central _ research program synthesis.", "central 2 research program synthesis.", "central s.a research program synthesis.", "central de research program synthesis."
"central tax research program stress." » "central tax research programs stress.", "central tax research project stress.", "central tax research program success.", "central bank research program stress.", "central _ research program stress.", "central 2 research program stress.", "central taxes research program stress."

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 a research program synthesis.") OR ("central tax research program stress."))~.
• Removing quotes may allow a broader search: (( central a research program synthesis. ) or ( central tax research program stress. ))~.
• Adding a wildcard symbol may retrieve word variants: (("central a research program synthesis.") or ("central tax research program stress."))*.