Perhaps you should try some spelling variations:
"agricultural introduction" » "agriculture introduction", "agricultural production", "agricultural productions"
"agricultural instruction" » "agriculture instruction", "agricultural institution", "agricultural reconstruction"

Try widening your search to All Fields.

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: (("agricultural introduction") OR ("agricultural instruction")).
• Removing quotes may allow a broader search: (( agricultural introduction ) or ( agricultural instruction )).
• Adding a wildcard symbol may retrieve word variants: (("agricultural introduction") or ("agricultural instruction"))*.