Perhaps you should try some spelling variations:
income distributions » income distribution, income redistribution, time distributions
stable distributions » size distributions
2f developing » f developing, self developing, turf developing

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 distributions) OR (stable distributions)) %2f developing countries%22.
• Adding a wildcard symbol may retrieve word variants: %((income distributions) or (stable distributions)) %2f developing countries%22*.