Perhaps you should try some spelling variations:
22income distribution » income distributions, income redistribution, genome distribution
2f developing » f developing, 2.3 developing, 2.2 developing
70 developing » 20 developing, 30 developing, 40 developing
10 developing » 10 development

Try widening your search to All Fields.

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• If you are trying to use Boolean operators, they must be ALL CAPS: %((22income distribution) OR (income distribution)) %((2f developing) OR (((70 developing) OR (10 developing)))) countries%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((22income distribution) or (income distribution)) %((2f developing) or (((70 developing) OR (10 developing)))) countries%22".
• Adding a wildcard symbol may retrieve word variants: %((22income distribution) or (income distribution)) %((2f developing) or (((70 developing) OR (10 developing)))) countries%22*.