(4) Bulgaria, Czechoslovakia, Hungary, Poland and the USSR: for products which include value added in the exporting preference-receiving country, enter the letter „Y“ in box 8 followed by the value of imported materials and components expressed as a percentage of the fob price of the exported products (example „Y“ 45 %); for products obtained in a preference-receiving country and worked or processed in one or more other such countries, enter „PK“.