Perhaps you should try some spelling variations:
communication cohesion » communication collections, communication control, communication cost
a extensions » 2 extensions, 3 extensions, c extensions
6 extensions » 2 extensions, 3 extensions, c extensions
_ extensions » _ extension
2 waves » _ waves, 3 waves, 2 wave

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

• Performing a fuzzy search may retrieve terms with similar spellings: communication cohesion ((((a extensions) OR (6 extensions))) or (_ extensions)) 2 waves~.
• If you are trying to use Boolean operators, they must be ALL CAPS: communication cohesion ((((a extensions) OR (6 extensions))) OR (_ extensions)) 2 waves.
• The words AND, OR and NOT may confuse the search; try adding quotes: "communication cohesion ((((a extensions) OR (6 extensions))) or (_ extensions)) 2 waves".
• Adding a wildcard symbol may retrieve word variants: communication cohesion ((((a extensions) OR (6 extensions))) or (_ extensions)) 2 waves*.