++++ Agriculture - Common organization of the markets - Milk and milk products - Additional levy on milk - Determination of reference quantities which are exempt from the levy - Special rules for producers who have adopted milk production development plans - Discretionary power of Member States as to whether or not to allocate special reference quantities - Limits - Conditions for grant fixed on the basis of objective criteria - Whether permissible ( Council Regulation No 857/84, Art . 3(1 ) )