Perhaps you should try some spelling variations:
"support trade integration theories." » "support trade integration theorems.", "support trade integrationstheorie 2.", "support trade integration theory.", "support trainer integration theories.", "export trade integration theories.", "import trade integration theories."
"supply grid irrigation systems." » "supply grain irrigation systems.", "supply drip irrigation systems.", "supply gray irrigation systems.", "supply crowd irrigation systems.", "supply great irrigation systems.", "support grid irrigation systems.", "supply grid irrigation system."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("support trade integration theories.") or ("supply grid irrigation systems."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("support trade integration theories.") OR ("supply grid irrigation systems.")).
• Removing quotes may allow a broader search: (( support trade integration theories. ) or ( supply grid irrigation systems. )).
• Adding a wildcard symbol may retrieve word variants: (("support trade integration theories.") or ("supply grid irrigation systems."))*.