Under normal circumstances, the fund invests at least 80% of its net assets (plus the amount of borrowings, if any) in, or derives at least 80% of its income from, municipal bonds. It may indirectly and directly invest in issuers located in U.S. territories, commonwealths, possessions or protectorates. The fund may invest in debt securities of any credit quality or maturity. It may invest up to 100% of its assets in below investment grade securities.