++++ COMMUNITY LAW - PRINCIPLES - EQUAL TREATMENT - DISCRIMINATION ON GROUNDS OF NATIONALITY - PROHIBITION - NATIONAL LEGISLATION ON THE PRICE OF BOOKS - DIFFERENCE OF TREATMENT IN FAVOUR OF RE-IMPORTED BOOKS - WHETHER PERMISSIBLE ( EEC TREATY, ART . 7 ) - 2 - FREE MOVEMENT OF GOODS - QUANTITATIVE RESTRICTIONS - MEASURES HAVING EQUIVALENT EFFECT - NATIONAL LEGISLATION ON THE PRICE OF BOOKS - DIFFERENCE OF TREATMENT IN FAVOUR OF RE-IMPORTED BOOKS - WHETHER PERMISSIBLE ( EEC TREATY, ART . 7 )