Perhaps you should try some spelling variations:
scientific exploration » scientific explanation, scientific application, scientific collaboration
african voyagers » african managers, african teenagers, african voices
american images » america images, america image, american wages

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 images) OR (african voyagers)) of scientific exploration.
• Adding a wildcard symbol may retrieve word variants: european and ((american images) or (african voyagers)) of scientific exploration*.