Perhaps you should try some spelling variations:
"resources research series" » "research research series", "reservices research series", "resciences research series", "redevices research series", "resources research services", "resources research theories", "resources research service"
"source research studies" » "source research study", "force research studies", "source search studies", "space research studies"
"sources research series" » "services research series", "sciences research series", "devices research series", "sources research services", "sources research theories", "sources research service"

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: (("source research studies") OR ((("sources research series") OR ("resources research series")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"source research studies\") or (((\"sources research series\") OR (\"resources research series\"))))".
• Removing quotes may allow a broader search: (( source research studies ) or ((( sources research series ) OR ( resources research series )))).
• Adding a wildcard symbol may retrieve word variants: (("source research studies") or ((("sources research series") OR ("resources research series"))))*.