Perhaps you should try some spelling variations:
"survey based immunization systems." » "survey based communication systems.", "survey based immunization rates.", "survey based immunization costs.", "survey basic immunization systems.", "survey mass immunization systems.", "survey measles immunization systems."
"supply grid irrigation schemes." » "supply grid irrigation scheme.", "supply grid irrigation systems.", "supply drip irrigation schemes.", "supply syria irrigation schemes.", "supply crop irrigation schemes.", "supply crowd irrigation schemes.", "support grid 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: (("supply grid irrigation schemes.") OR ("survey based immunization systems."))~.
• Removing quotes may allow a broader search: (( supply grid irrigation schemes. ) or ( survey based immunization systems. ))~.
• Adding a wildcard symbol may retrieve word variants: (("supply grid irrigation schemes.") or ("survey based immunization systems."))*.