Perhaps you should try some spelling variations:
income distributions » income redistribution, time distributions, discrete distributions
self developing » relief developing, self development, level developing
f developing » turf developing, 7.2 developing, 7.1 developing

Try widening your search to All Fields.

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: %((income distribution) OR (income distributions)) %((self developing) OR (f developing)) countries%22.
• Adding a wildcard symbol may retrieve word variants: %((income distribution) or (income distributions)) %((self developing) or (f developing)) countries%22*.