93. Whenever, under this Ordinance or any rule made hereunder, the doing or the omitting to do anything or the validity of anything depends upon the approval, sanction, consent, concurrence, declaration, opinion or satisfaction of-(a) the Authority or the Chairman, or (b) any employee of the Authority,a written document, signed, in case (a) by the Chairman, and in case (b) by the said employee, purporting to convey or set forth such approval, sanction, consent, concurrence, declaration, opinion or satisfaction, shall be sufficient evidence of such approval, sanction, consent, concurrence, declaration, opinion or satisfaction.