Perhaps you should try some spelling variations:
efficiency education » efficiency reduction, efficiency induction, efficiency mutation
efficiency equation » efficiency evaluation, efficiency reduction, efficiency situation
efficient education » efficient educational, efficient medication, efficient reduction

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 education))))%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((efficiency equation) or (((efficiency education) OR (efficient education))))%22".
• Adding a wildcard symbol may retrieve word variants: %((efficiency equation) or (((efficiency education) OR (efficient education))))%22*.