Perhaps you should try some spelling variations:
irrigation system » irrigation systems, irrigation water, irrigation scheme
banking series » banking services, banking service, banking securities
banking crises » banking services
improve state » improved stove, improved space, improve water
export scale » export share, export sales, export shares

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( export scale irrigation system. ) or ( improve state ((banking series) or (banking crises)). ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( export scale irrigation system. ) OR ( improve state ((banking series) OR (banking crises)). )).
• Adding a wildcard symbol may retrieve word variants: (( export scale irrigation system. ) or ( improve state ((banking series) or (banking crises)). ))*.