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))*.