Perhaps you should try some spelling variations:
binomial distribution » spatial distribution
income distributions » income redistribution, time distributions, discrete distributions
72 developing » 7.2 developing, 762 developing, 2 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 distribution) OR (binomial distribution))) OR (income distributions)) %72 developing countries%22.
• Adding a wildcard symbol may retrieve word variants: %((((income distribution) or (binomial distribution))) or (income distributions)) %72 developing countries%22*.