It shall be the duty of the governing bodies of such cities during each year to levy taxes sufficient to pay the interest on such bonds and to create a sinking fund to pay said bonds at the date of maturity thereof. Said sinking fund may be invested in the investments authorized by K.S.A. 12-1675, and amendments thereto, in the manner prescribed therein or in the bonds herein provided for or county or municipal bonds.
K.S.A. 73-436