Each of the previous waves had come in response to a profound shift in the real economy.

Moreover, the previous waves occurred during periods when the economy and economic theory were much less highly developed.

The horror was a crawling thing which must have been cast up by a previous wave.

The foam swirled into the air in sheets as it met the backwash of the previous wave.

Though there have been previous waves of suicide attacks, it is unusual for Palestinian groups to conduct two in one day.

There, it combined with an area of disturbed weather due to two previous tropical waves.

Or some previous wave of colonists, who passed through this system.

"They look a bit more ragged and dirty than the previous wave, but still in reasonably good shape."

Each wave is faster, by a factor of 10, than the previous wave.

Therefore each wave takes slightly less time to reach the observer than the previous wave.