Mich. Comp. Laws § 38.1215

Sec. 5. The legislative body of a public corporation may, by resolution, allow a trust to invest the assets of the trust in accordance with the public employee retirement system investment act, 1965 PA 314, MCL 38.1132 to 38.1140. The resolution shall include the following: (a) A statement of the authority under which the trust is established. (b) Approval to invest the assets of the trust in accordance with the public employee retirement system investment act, 1965 PA 314, MCL 38.1132 to 38.1140.