Perhaps you should try some spelling variations:
learning inequality » measuring inequality, deepening inequality, reducing inequality
garding inequality » garding's inequality, hardy inequality, hardy's inequality
learning quality » learning ability
wage » wave
earnings » warning

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: wage AND ((((learning inequality) OR (((garding inequality) OR (earnings inequality))))) OR (learning quality)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "wage and ((((learning inequality) or (((garding inequality) OR (earnings inequality))))) or (learning quality))".
• Adding a wildcard symbol may retrieve word variants: wage and ((((learning inequality) or (((garding inequality) OR (earnings inequality))))) or (learning quality))*.