Perhaps you should try some spelling variations:
learning inequality » learning quality, measuring inequality, deepening inequality
holder's inequality » hardy's inequality
garding inequality » garding's inequality, hardy inequality, hardy's inequality
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 (earnings inequality))) OR (((garding inequality) OR (holder's inequality)))).
• Adding a wildcard symbol may retrieve word variants: wage and ((((learning inequality) or (earnings inequality))) or (((garding inequality) or (holder's inequality))))*.