Government Code § 29968

If the bonds mature at one time, the annual tax levy shall be sufficient to pay the interest on the bonds as it comes due and create a sinking fund for the payment of the principal on or before maturity. The sum to be raised each year and placed in the sinking fund for the payment of the principal of the bonds shall not be less than an amount obtained by dividing the total principal amount of the bonds issued by the total number of years the bonds are to run.