23. Plaintiffs (or defendants) may authorize one of them to act for them

23. When there are more plaintiffs than one, any one or more of them may be authorized by any other of them to appear, plead, or act for such other in any proceeding under this Ordinance, and in like manner, when there are more defendants than one, any one or more of them may be authorized by any other of them to appear, plead, or act for such other in any such proceeding. The authority shall be in writing signed by the party giving it, and shall be filed in court.