Perhaps you should try some spelling variations:
"support carbon integration theory." » "support carlo integration theory.", "support urban integration theory.", "support can integration theory.", "support carbon integration through.", "support carbon information theory.", "support carbon innovation theory.", "supporting carbon integration theory.", "support common integration theory."
"support crop irrigation schemes." » "support crop irrigation scheme.", "support crop irrigation systems.", "support drip irrigation schemes.", "support scale irrigation schemes.", "support canal irrigation schemes.", "support crops irrigation schemes.", "support cross irrigation schemes.", "support across 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: (("support carbon integration theory.") OR ("support crop irrigation schemes."))~.
• Removing quotes may allow a broader search: (( support carbon integration theory. ) or ( support crop irrigation schemes. ))~.
• Adding a wildcard symbol may retrieve word variants: (("support carbon integration theory.") or ("support crop irrigation schemes."))*.