Perhaps you should try some spelling variations:
"elter regional convergence" » "elter global convergence", "better regional convergence", "center regional convergence", "inter regional convergence"
"elter regional reference" » "elter regional conference", "elter regional resilience", "better regional reference", "center regional reference", "inter regional reference"
"elter regional differences" » "better regional differences", "center regional differences", "inter regional differences"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"elter regional reference\") OR (((\"elter regional convergence\") OR (\"elter regional differences\"))))".
• Removing quotes may allow a broader search: (( elter regional reference ) OR ((( elter regional convergence ) OR ( elter regional differences )))).
• Adding a wildcard symbol may retrieve word variants: (("elter regional reference") OR ((("elter regional convergence") OR ("elter regional differences"))))*.