Some sleep for long periods, others in short bursts.

Some sleep for long periods, others in short bursts.

From the other two, there were signs of sleep -- brief periods of activity alternating with periods of silence.

From the other two, there were signs of sleep — brief periods of activity alternating with periods of silence.

From the other two, there were signs of sleep -- brief periods of activity alternating with periods of silence.

Availability to travel in Europe for short periods.

They say there's long periods of boredom followed by short periods of excitement.

It has long stretches of boring time interrupted by brief periods of intense excitement.

It involves short bursts of activity followed by periods of lower activity.

These long, frigid periods were interrupted by relatively brief periods of warming.

Bulgaria has had few periods of complete independence.

They can play with other children for short periods of time.

On short time periods, the resolution error dominates.

Available for all year, but only for short periods.

When it does rain it is usually only for brief periods.