Perhaps you should try some spelling variations:
measuring inequality » measuring quality
deepening inequality » explaining inequality, earnings inequality, reducing inequality
learning inequality » earnings inequality, garding inequality, reducing inequality
learning quality » learning ability

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