Mont. Code Ann. § 7-7-4311

In order to issue bonds to refund bonds theretofore issued and outstanding, it shall only be necessary for the council, at a regular or duly called special meeting, to pass and adopt a resolution setting forth the facts with regard to the indebtedness to be refunded, showing the reason for issuing such refunding bonds and fixing and determining the details thereof, including whether the bonds will be sold at a private negotiated sale or public sale.