At the end of September, investors in Vanguard Group's mutual funds will no longer be able to buy shares of funds they had sold within the previous 60 days by phone or Internet. Instead, investors can send in a check by mail, the Associated Press reports.

The move is intended to reduce transaction costs for shareholders and make the funds more manageable by reducing frequent trading. It will also strengthen "existing safeguards that help protect our mutual-fund shareholders from the potentially harmful effects of frequent trading and market-timing," the company said on its Web site.

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