Perhaps you should try some spelling variations:
learning inequality » earnings inequality, learning quality, measuring inequality
garding inequality » garding's inequality, earnings inequality, hardy inequality
learning ability » learning disability, learning activity, learning about

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 (learning ability))) OR (garding inequality)).
• Adding a wildcard symbol may retrieve word variants: (wage or wave) and ((((learning inequality) or (learning ability))) or (garding inequality))*.