Perhaps you should try some spelling variations:
irrigation systemss » irrigation system, irrigation schemes, navigation systems
rural irrigation » canal irrigation, local irrigation, total irrigation
case irrigation » scale irrigation, change irrigation, canal irrigation
supply rural » supply curve
supply case » supply cost, supply chain, supply curve
systems. » system.
systemss. » systems.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( supply case irrigation systems. ) or ( supply rural irrigation systemss. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( supply case irrigation systems. ) OR ( supply rural irrigation systemss. )).
• Adding a wildcard symbol may retrieve word variants: (( supply case irrigation systems. ) or ( supply rural irrigation systemss. ))*.