Perhaps you should try some spelling variations:
communications communication » communication communication, communicating communication, communication communicating
communication based » communication between
based dispersion » wave dispersion, gas dispersion, based discussion
index theorem » index theory
index tree » index time, indexing tree, index stress
index free » index from

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

• Performing a fuzzy search may retrieve terms with similar spellings: communications communication based dispersion ((((index tree) OR (index free))) or (index theorem))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: communications communication based dispersion ((((index tree) OR (index free))) OR (index theorem)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "communications communication based dispersion ((((index tree) OR (index free))) or (index theorem))".
• Adding a wildcard symbol may retrieve word variants: communications communication based dispersion ((((index tree) OR (index free))) or (index theorem))*.