Perhaps you should try some spelling variations:
"export trade integration theories." » "export trade integration theorems.", "export trade integrationstheorie 2.", "export trade integration theory.", "export taxes integration theories.", "export base integration theories.", "export tax integration theories."
"support change irrigation schemes." » "support change irrigation scheme.", "support change irrigation systems.", "support change mitigation schemes.", "support canal irrigation schemes.", "support large irrigation schemes.", "support chapter irrigation schemes.", "support can irrigation schemes.", "support chuan irrigation schemes."

Try widening your search to All Fields.

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

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