Extension of customs exemption notification: expiry date substituted under Customs Act powers to prolong its operation. Amendment substitutes the figures, letters and words '31st day of December, 1987' in paragraph 2 of Notification No. 291/84-Customs with '31st day of December, 1990', extending the notification's operative period under the statutory power in sub-section (1) of section 25 of the Customs Act, 1962, on grounds of public interest.