Perhaps you should try some spelling variations:
2.1 communication » 2.14 communication, 2.3 communication, 2.7 communication
technology trade » technology trends, technology transfer, technology transfers
trade population » create population, france population, age population
4 developpement » de developpement, le developpement, et developpement
population per » population panel, population p230, population area
des afrique » en afrique, de l'afrique
per fig » per firm
fig 2.1 » fig 12.1, fig 4.1, fig 5.1
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 trade population per fig 2.1 communication costs 4 developpement des afrique.*.