The investment seeks to provide current income exempt from regular federal income tax, consistent with the maturity and quality standards, and to preserve capital. The fund will invest at least 80% of its assets in, or derive at least 80% of its income from, securities that are exempt from regular federal income tax and that do not subject the investors to federal alternative minimum tax. It invests primarily in debt securities rated A- or better or A3 or better, or unrated but determined by the fund's investment adviser to be of equivalent quality. The dollar-weighted average effective maturity of the fund's portfolio is between three and 10 years.