Perhaps you should try some spelling variations:
scientific exploration » scientific explanation, scientific application, scientific collaboration
african teenagers » american teenagers, african managers, african teachers
american voyages » american villages, aerial voyages, african voyagers

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

• If you are trying to use Boolean operators, they must be ALL CAPS: european AND ((american voyages) OR (african teenagers)) of scientific exploration.
• Adding a wildcard symbol may retrieve word variants: european and ((american voyages) or (african teenagers)) of scientific exploration*.