Perhaps you should try some spelling variations:
oral communication » personal communication
der developpement » de developpement, des developpements, leur developpement
developpement en » developpement et, developpement des, developpement de
der variation » de variation, does variation, die variation
variation der » variation des, variation bei, variation _
a der » _ der, 2 der, 3 der
theorie » theories

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

• Adding a wildcard symbol may retrieve word variants: theorie der variation der items oral communication a der developpement en afrique.*.