Perhaps you should try some spelling variations:
international convention » international context, international communication, international conference
based extension » based extraction
extension codes » extension modes, extension costs, extension model
codes waves » bodies waves, models waves, modes wave
cooperation » operation

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((international cooperation) or (international convention)) based extension codes waves~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((international cooperation) OR (international convention)) based extension codes waves.
• Adding a wildcard symbol may retrieve word variants: ((international cooperation) or (international convention)) based extension codes waves*.