The face of each revenue bond shall state:
(a) That the payment or redemption of the bond and the payment of the interest thereon is secured solely by a first and direct charge and lien upon all or the portion, as prescribed by the district by order or by contract, of the revenues pledged therefor.
(b) That neither the payment of all or any part of the principal or interest thereon is a general debt, liability, or obligation of the district.
(c) That the bond is subject to call and redemption prior to maturity, if the board has so provided.