To do this over a long period of time is a major technical challenge.

Each study attends to the treatment of a particular technical challenge.

However, they quickly found themselves up against a host of technical challenges.

"At first I got caught up in representation as a technical challenge," he says.

Then would come the technical challenge of building a huge system unlike anything now in existence.

"Our position has always been that we would not make technical challenges," he said.

The researchers are still working out what she calls "technical challenges" with the technology.

The building of the track and the station in the years 1968-74 represented a special technical challenge.

Even with all these ideas coming about there are still some technical challenges that remain.

Beyond the technical challenges, of course, are more daunting business issues.