Extension of exemption period under Customs Act by substituting the notification expiry date to a later date. Amendment to Notification No. 257/86-Customs substitutes the expiry date in paragraph 2, extending the period of the Soda Ash exemption by replacing the earlier specified date with a later date; the change is effected under the authority of sub-section (1) of section 25 of the Customs Act, 1962.