Perhaps you should try some spelling variations:
efficiency education » efficiency reduction, efficient education, efficiency induction
efficiency equation » efficiency evaluation, efficiency reduction, efficiency situation
efficient reduction » efficient production, efficient prediction, efficient detection

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

• If you are trying to use Boolean operators, they must be ALL CAPS: %((efficiency equation) OR (((efficiency education) OR (efficient reduction))))%22.
• Adding a wildcard symbol may retrieve word variants: %((efficiency equation) or (((efficiency education) or (efficient reduction))))%22*.