However it is also the principal cause of their weaknesses.

Yet neither air nor water is the principal cause of sound.

The appearance of the crisis in America shows that they cannot be its principal causes.

The principal cause is almost certainly the way personal computers are now sold.

In an article published on March 13, 2012 he discussed "the principal cause of higher oil prices."

The principal causes of the changes in costs over recent years are well-known.

The principal cause, according to the experts, is the absence of parents.

The principal cause of water scarcity is the growth in demand.

There has to be an effect - even if it's not the principal cause.

But energy was the principal cause, he said, "and that's beginning to back off."