Perhaps you should try some spelling variations:
5.2 communication » 3.2 communication, 6.2 communication, 2.2 communication
population class » population case, population census, population access
technology eimt » technology ecit, technology e, technology equipment
eimt population » em population, list population, host population
class barriers » glass barriers, crash barriers, access barriers
developing en » developing e, developing eq, developing egg
barriers 5.2 » barriers 3.2, barriers 4.2, barriers 5.7
4 developing » 3 developing
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 eimt population class barriers 5.2 communication costs 4 developing en afrique.*.