Perhaps you should try some spelling variations:
"central a research program synthesis." » "central a research programs synthesis.", "central _ research program synthesis.", "central tax research program synthesis.", "central s.a research program synthesis."
"central 2 research project stress." » "central 2 research projects stress.", "central 2 research project success.", "central 2 research project sites.", "central _ research project stress.", "central de research project 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 2 research project stress."))~.
• Removing quotes may allow a broader search: (( central a research program synthesis. ) or ( central 2 research project stress. ))~.
• Adding a wildcard symbol may retrieve word variants: (("central a research program synthesis.") or ("central 2 research project stress."))*.