Export duty exemption for sugar under Advance Authorization allowed, subject to proportional import, no domestic procurement, and documentary proof at clearance. Amendment inserts a Nil duty entry exempting sugar exported under a valid Advance Authorization issued by the Director General of Foreign Trade or an authorized officer, subject to conditions: exports in proportion to imported raw sugar under the Authorization; Authorization not invalidated; no procurement of raw sugar from the domestic market; and submission at port clearance of a bill of entry evidencing import under the Authorization to the jurisdictional proper officer of customs.