Wis. Stat. § 231.18: Investment authorization.

The notes and bonds of the authority are securities in which all public officers and bodies of this state and all political subdivisions and public officers thereof, all banks, trust companies, savings banks and institutions, savings and loan associations, investment companies and all personal representatives, guardians, trustees and other fiduciaries may legally invest any sinking funds, moneys or other funds belonging to them or within their control.