There are three principal ways in which discretion can be controlled.

One of the principal ways to gain points is through energy saving measures.

"The principal way we carry out our responsibilities is to keep track of people," he said.

There are two principal ways to do this through voting:

There are three principal ways of providing oxygen to the space station.

Yet until recently this was one of the principal ways in which beauty was discussed.

Government can run afoul of that prohibition in two principal ways.

The current system will be improved in four principal ways.

There are three principal ways to secure a wireless network.

There are two principal ways in which eruptions can be grouped.