Perhaps you should try some spelling variations:
communication costly » communication costs, communication costa, communications costs
trade developpement » trade developement, trade development, de developpement
3.5 communication » 3.2 communication, 3 communication, 2.3 communication
developpement en » developpement et, developpement des, developpement de
inflation bayes » inflation rates, inflation taxes, inflation boys
costly trade » costs trade, country trade, costly than
rule 3.5 » rule 2.5, rule 3.1, rule 3.2

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

• Adding a wildcard symbol may retrieve word variants: technology _ inflation bayes rule 3.5 communication costly trade developpement en afrique.*.