Perhaps you should try some spelling variations:
rural retention » rural reflection, rural extension, metal retention
rural education » moral education, formal education, legal education
1998 brazilian » 19th brazilian, 18 brazilian, 12th brazilian

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: 1998 brazilian ((rural retention) OR (rural education)).
• Adding a wildcard symbol may retrieve word variants: 1998 brazilian ((rural retention) or (rural education))*.