Gov. Code, § 6558

The indenture may include covenants or other provisions, other than or in lieu of the provisions required by Article 1 (commencing with Section 6500) of this chapter, relating to the collection, deposit and safekeeping of the revenues, the permissible uses thereof, the special fund or funds to be kept for the payment of principal and interest of the bonds, including reserve, sinking, bond service, redemption and trust funds, and any bond payable from the revenue fund may be paid from any such special fund set up therefor; the appointment of a trustee; the permissible investments for moneys in said funds, or any thereof, the accounts and records to be kept, audits thereof and examination thereof by bondholders and others, and reports to be made by the entity. Any indenture providing for the appointment of a trustee shall limit such trustee’s power of investment to only such investments as are authorized by Section 53601.