S.D. Codified Laws § 5-12-27.1
Refunding bonds authorized--Purposes
The Building Authority may issue negotiable refunding bonds to refund:
(1) Unpaid matured bonds;
(2) Unpaid matured coupons evidencing interest upon its unpaid matured bonds; and
(3) Interest at the coupon rate upon its unpaid matured bonds that has accrued since the maturity of these bonds.
Source: SL 1975, ch 50, § 1.