The 18 teams are divided into three groups of six and each group plays a double round-robin tournament.

According to the regulations, each of the six participants plays two games against every other, thus making it a double round-robin tournament.

Currently, it is composed by 14 clubs playing a double round-robin tournament.

The ten teams competed in a double round-robin tournament, one game at home and one away.

The six qualified team competed in a double round-robin tournament.

Between 1931 and 1966 it was played during one year in a double round-robin tournament.

The 1942-43 tournament was played by seven teams in a double round-robin tournament.

For the 1939, 1940, and 1941 seasons, teams played all others twice instead-a double round-robin tournament.

They played a double round-robin tournament with four teams who won the playoffs from the third-tier league Division 1.

The league is played out as a double round-robin tournament.