Okla. Stat. tit. 62, § 62-399: Sinking fund - How computed - Installment bonds

It shall be the duty of every county, city, town, township, the

board of education of any city, and of every school district,

issuing bonds under this article, and of the proper officers

thereof, to create a sinking fund; and there shall be levied by the

proper officers, annually, a sufficient tax therefor for the

redemption of such bonds, which shall be collected as other taxes,

and paid into the treasury as provided by law for other taxes, and

shall remain as a specific fund for the redemption of said bonds;

the amount of which sinking fund shall be as follows: In every

instance in which bonds shall be issued under this article, for

twenty (20) years or less, the quotient found by dividing the amount

of the principal of such bonds by such number of years shall be the

amount of sinking fund to be levied each year for the redemption of

such bonds; but in every instance in which such bonds shall be

issued for more than twenty (20) years, it shall not be necessary to

create a sinking fund, or to levy a tax therefor, until the

twentieth year prior to maturity of such bonds, at which time, and

each year thereafter one-twentieth (1/20) of the principal amount of

such bonds shall be levied as a sinking fund for the redemption of

such bonds: Provided, that any county, city, town township, the

board of education of any city, or any school district, issuing

bonds under this article, may buy in and cancel any such bonds

whenever the same can be done at or below par: Provided, further,

that such sinking fund, when not required for the payment or

purchase of bonds, may be invested in bonds of the United States or

of the State of Oklahoma, and in no other manner: And provided,

further, that under the provisions of this article, the proper

officers are authorized, if desirable, to issue installment bonds,

running twenty-five (25) years, having coupons attached,

representing the semiannual interest to become due thereon; and each

coupon attached to any installment bond shall, after five (5) years

from its date, represent one-fortieth (1/40) of its principal, which

amount shall be shown by separate words and figures aside from the

interest represented in the coupon; and each installment bond shall

show upon its face that its principal is included in its coupons.