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. It will not invest in securities that subject the investors to federal alternative minimum tax. It invests at least 65% in debt securities rated A- or better or A3 or better by Nationally Recognized Statistical Rating Organizations designated by the fund's investment adviser, or unrated but determined by the fund's investment adviser to be of equivalent quality.