Perhaps you should try some spelling variations:
"economic reactions" » "economic relations", "economic sanctions", "economic functions"
"economic sections" » "economic section", "economic sanctions", "economic sectors"
"dynamics system" » "dynamic system", "dynamical system", "dynamic systems"

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: (("dynamics system") OR ((("economic sections") OR ("economic reactions")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"dynamics system\") or (((\"economic sections\") OR (\"economic reactions\"))))".
• Removing quotes may allow a broader search: (( dynamics system ) or ((( economic sections ) OR ( economic reactions )))).
• Adding a wildcard symbol may retrieve word variants: (("dynamics system") or ((("economic sections") OR ("economic reactions"))))*.