Wagon trains -- groups of wagons -- rode in four lines across the land when they passed through dangerous country.

VOA: special.2009.03.30

The two groups were retested four years later, and the study compared the results with the first test.

VOA: special.2009.10.21

The competition is organized so the thirty-two teams play in eight groups,each with four teams.

VOA: special.2010.06.09

The students played in groups of four.

VOA: special.2009.10.21