The fund, under normal circumstances, invests at least 80% of its assets in municipal bonds, the income from which is exempt from federal income tax. It will seek to maintain a portfolio dollar-weighted average duration of 3 to 10 years, although the fund may invest in instruments of any duration or maturity. The manager will invest, under normal circumstances, at least 65% of its net assets in investment grade quality bonds as rated by a nationally recognized statistical rating organization, or if unrated, judged to be of comparable quality the fund's subadvisor.