Perhaps you should try some spelling variations:
learning inequality » earnings inequality, learning quality, garding inequality
hardy's inequality » hardy inequality, holder's inequality, harnack inequality
warning inequality » earnings inequality, garding inequality, widening inequality
wage » wave

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 (((hardy's inequality) OR (warning inequality)))).
• Adding a wildcard symbol may retrieve word variants: wage and ((learning inequality) or (((hardy's inequality) or (warning inequality))))*.