A very challenging and exciting new area of science has thus now appeared on the scene.

In challenging areas, why not make the cells smaller and reduce power by bringing them to the users?

The flight test program has yet to explore the most challenging areas.

It is predicted that this will be the most challenging area for business in the '90s.

Based in challenging areas, Harris schools have produced some outstanding results and are a real example of what can be achieved.

However, Ofsted also finds evidence of great schools in challenging areas.

The most challenging area of all is high above Wasdale.

This will be one of the most challenging areas for Hughes.

You know, therefore, the progress that has been made during the past six months and what remains to be done in many challenging areas.

"Since as long as I can remember, this is the most challenging area," he said.