(8)The Central Government, if it considers necessary or expedient so to do, may, by notification in the Official Gazette, direct that the deduction allowable under this section shall not be allowed in respect of any ship or aircraft acquired or any machinery or plant installed after such date] [Inserted by Act 66 of 1976, Section 8 (w.e.f. 1.4.1976).] [* * *] [ Certain words omitted by Act 23 of 1986, Section 7 (w.e.f. 1.4.1986).] as may be specified therein.