Perhaps you should try some spelling variations:
"cure research studies" » "cure research study", "curve research studies", "care research studies", "case research studies"
"core research series" » "core research services", "core research theories", "core research service", "care research series", "more research series", "case research series"

Try widening your search to All Fields.

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: (("cure research studies") OR ("core research series")).
• Removing quotes may allow a broader search: (( cure research studies ) or ( core research series )).
• Adding a wildcard symbol may retrieve word variants: (("cure research studies") or ("core research series"))*.