21.   The practice has been outlawed and a voluntary ban was imposed two weeks before the show aired.

22.   The SEC could also try to orchestrate a voluntary ban on such donations within the industry, as it did before issuing its rule a few years ago.

23.   The voluntary ban was a success.

24.   The United States has been operating under a voluntary ban on testing, and will continue to do so, White House officials insist.

25.   The voluntary ban has been organized by two environmental organizations, SeaWeb and the Natural Resources Defense Council.

26.   The voluntary ban comes as many nonsmokers have been complaining about smokers in the park.

27.   The voluntary ban was dramatically successful in its first year.

28.   Unfortunately, the liquor industry has abandoned its own voluntary ban on advertising on television, the medium most likely to reach vast numbers of potential underage drinkers.

29.   Vendors appeared to be complying with the voluntary ban Wednesday.

30.   A global treaty barring rich countries from dumping toxic waste in the Third World went into effect last September, reinforcing an existing voluntary ban.