Perhaps you should try some spelling variations:
models communications » modern communications, modern communication, zones communications
communications costs » communication costs, communications _
de developpement » sme development
developpement de » developpement des, developpement durable
study selection » student selection
selection a » selection _, selection bias, selection 3.2
de afrique » de l'afrique, en afrique, l afrique
costs de » costs _, costs 4, costs a
a based » a biased, na based, a base

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

• Adding a wildcard symbol may retrieve word variants: technology study selection a based models communications costs de developpement de afrique.*.