Commission Regulation (EC) No 1680/98 of 29 July 1998 amending Regulations (EC) No 936/97 opening and providing for the administration of tariff quotas for high-quality fresh, chilled and frozen beef and for frozen buffalo meat and (EEC) No 139/81 defining the conditions for the admission of certain kinds of frozen beef and veal to subheading 0202 30 50 of the Combined Nomenclature