Perhaps you should try some spelling variations:
"export trade integration theories." » "export trade integration theory.", "export trade integration through.", "export trade integration efforts.", "export share integration theories.", "export taxes integration theories.", "export price integration theories."
"import data irrigation schemes." » "import data irrigation scheme.", "import data irrigation systems.", "import canal irrigation schemes.", "import water irrigation schemes.", "import spate irrigation schemes.", "import duty irrigation schemes."

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: (("import data irrigation schemes.") OR ("export trade integration theories."))~.
• Removing quotes may allow a broader search: (( import data irrigation schemes. ) or ( export trade integration theories. ))~.
• Adding a wildcard symbol may retrieve word variants: (("import data irrigation schemes.") or ("export trade integration theories."))*.