The board or its executive director may delegate by contract to private sector or other external advisors or managers the discretionary authority, as fiduciaries, to purchase or otherwise acquire, sell, or otherwise dispose of or manage investments or investment properties on behalf of the board, subject to investment or management criteria established by the board or its executive director. Such criteria relevant to particular investments or class of investment applicable under the board's contract with an advisor or manager must be incorporated by reference into the contract.