(a)issue notice to such person requiring him to furnish within such period, as may be specified in the notice, the return of income in respect of each assessment year falling within six assessment years and for the relevant assessment year or years referred to in clause (b), in the prescribed form and verified in the prescribed manner and setting forth such other particulars as may be prescribed and the provisions of this Act shall, so far as may be, apply accordingly as if such return were a return required to be furnished under section 139;