Section 17(3)(d) in The Air (Prevention And Control Of Pollution) (Union Territories) Rules, 1983
(d)Every appeal shall be submitted in quadruplicate to the Appellate Authority by the appellant or his authorised agent in person or sent to such Authority by registered post. When the appeal is presented by an agent duly authorised by the appellant, it shall be accompanied by a letter of authority written on a stamped paper of the value as required by law, appointing him as such an agent.