Perhaps you should try some spelling variations:
population center » population census, population censuses, population change
3.2 communication » 3 communication, 2.3 communication, de communication
technology 4 » technology _, technology 1, technology 3
4 population » 2 population, 2.1 population, 2.2 population
4 developing » 3 developing
center area » center crec, center based, center agent
area 3.2 » area 2.2, area 4.2, area 3.3
costs 4 » costs _, costs a, costs 4.2

You may be able to get more results by adjusting your search query.

• Adding a wildcard symbol may retrieve word variants: technology 4 population center area 3.2 communication costs 4 developing _ african.*.