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 case irrigation systems." » "supply scale irrigation systems.", "supply use irrigation systems.", "supply change irrigation systems.", "supply cost irrigation systems.", "supply chain irrigation systems.", "supply curve irrigation systems.", "supply case 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 case irrigation systems."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("support trade integration theories.") OR ("supply case irrigation systems.")).
• Removing quotes may allow a broader search: (( support trade integration theories. ) or ( supply case irrigation systems. )).
• Adding a wildcard symbol may retrieve word variants: (("support trade integration theories.") or ("supply case irrigation systems."))*.