Perhaps you should try some spelling variations:
communications convention » communications connections, communication connection, communication conversation
users dimensioning » systems dimensioning, user dimension, users designing
convention users » convention des, convention using, conversion user
database under » databases under, database index, database order
database user » databases user, database using, database based

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

• Performing a fuzzy search may retrieve terms with similar spellings: communications convention users dimensioning ((database under) or (database user))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: communications convention users dimensioning ((database under) OR (database user)).
• Adding a wildcard symbol may retrieve word variants: communications convention users dimensioning ((database under) or (database user))*.