Perhaps you should try some spelling variations:
integration theories » integration theory, integration through, integration efforts
irrigation schemes » irrigation scheme, irrigation systems
canal irrigation » scale irrigation
supply trade » supply side, supply case
supply canal » supply annual, supply rural, supply case

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: (( supply trade integration theories. ) OR ( supply canal irrigation schemes. ))~.
• Adding a wildcard symbol may retrieve word variants: (( supply trade integration theories. ) or ( supply canal irrigation schemes. ))*.