Perhaps you should try some spelling variations:
income distributions » income redistribution, time distributions, discrete distributions
self developing » relief developing, level developing
f developing » 7 developing, turf developing, f development

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 (self development))) OR (f developing)) countries%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((income distribution) or (income distributions)) %((((self developing) OR (self development))) or (f developing)) countries%22".
• Adding a wildcard symbol may retrieve word variants: %((income distribution) or (income distributions)) %((((self developing) OR (self development))) or (f developing)) countries%22*.