Any municipality which did not join in the incorporation of an authority may become a constitutent part thereof by amendment to the articles of incorporation adopted by the legislative body of such municipality and by the legislative body of each municipality of which such authority is composed. Other amendments may be made to the articles of incorporation if adopted by the legislative body of each municipality of which the authority is composed. Any such amendment shall be indorsed, published, and certified printed copies filed, in the same manner as the original articles of incorporation, except that the printed copies shall be certified and filed by the recording officer of the authority.