++++ SOCIAL POLICY - EUROPEAN SOCIAL FUND - AID FOR RECRUITMENT AND EMPLOYMENT OF YOUNG PEOPLE UNDER 25 - AMOUNT OF ASSISTANCE CALCULATED "PER PERSON AND PER UNIT OF TIME" - DETERMINATION OF THE UNIT OF TIME BY THE COMMISSION - DECISION 83/621 - CHOICE OF A WEEK AS THE UNIT OF TIME WITHOUT ANY APPARENT POSSIBILITY OF A REDUCTION OF THE AMOUNT FOR PART-TIME WORK - INTRODUCTION OF SUCH A REDUCTION DURING THE COURSE OF THE FINANCIAL YEAR - PRINCIPLE OF THE PROTECTION OF LEGITIMATE EXPECTATIONS - BREACH ( COUNCIL REGULATION NO 2950/83, ART . 2*(2 ); COMMISSION DECISION 83/621 )