Any city may join with the county or township in which such city is located in the joint erection or purchase of memorial buildings or monuments and suitable ground and equipment therefor, and the maintenance thereof, providing the council of such city and the board of supervisors of such county or the township trustees can so agree, but in cases where commissioners have already been appointed under section 37.9, such agreement shall be between such commissioners, but if only one of such parties has appointed commissioners, then such agreement shall be between the commissioners already appointed and the council of such city or the board of supervisors of such county or the township trustees, as the case may be.