On receipt of a reference under sub-section (1) of ¹ [section 8 or sub-section (1) of section 8A] the Tribunal shall serve on the person named in such reference, a notice, accompanied by a copy of such reference, calling upon him to make, within a period of thirty days from the date of receipt of such notice, such representation with regard to the averments made in the reference, and to produce such evidence as he may think fit in support of his defence:
     Provided that if the Tribunal is satisfied that the person aforesaid was prevented by sufficient cause from making his representation and from producing evidence in support of his defence within the said period of thirty days, it may permit him to make his representation and to produce evidence in support of his defence, within such further period, not exceeding thirty days, as it may, by order, specify.