21 DECEMBER 1967 , CONSISTING IN THE OBLIGATION ON THE PART OF AN EMPLOYED PERSON WHO WISHES TO REGULARIZE HIS PERIODS OF STUDY TO PROVE THAT HE EXERCISED , IMMEDIATELY AFTER SUCH PERIODS , A PROFESSIONAL OR TRADE ACTIVITY IN BELGIUM , IS AFFECTED BY ARTICLE 9 ( 2 ) OF REGULATION NO 1408/71 AS BEING A CLAUSE UNDER WHICH ADMISSION TO VOLUNTARY OR OPTIONAL CONTINUED INSURANCE IS MADE CONDITIONAL UPON THE OBLIGATION TO COMPLETE AN INSURANCE PERIOD , OR BY ANY OTHER PROVISION OF A COMMUNITY REGULATION .
7 THE SECOND QUESTION ASKS WHETHER , IF THE FIRST QUESTION IS ANSWERED IN THE NEGATIVE , THE EMPLOYED PERSON OF BELGIAN NATIONALITY CAN CLAIM EITHER EQUALITY OF TREATMENT UNDER ARTICLE 3 ( 1 ) OF REGULATION NO 1408/71 OR TO HAVE TAKEN INTO CONSIDERATION THE PERIOD OF INSURANCE COMPLETED UNDER BELGIAN LEGISLATION WITHIN THE MEANING OF ARTICLE 45 ( 1 ) OF THE SAME REGULATION , THAT IS , FOR THE ACQUISITION , RETENTION OR RECOVERY OF THE RIGHT TO BENEFITS OF OLD-AGE AND DEATH INSURANCE ( PENSIONS ), OR UNDER ANY OTHER PROVISION OF COMMUNITY LAW .
8 ARTICLE 9 ( 2 ) OF REGULATION NO 1408/71 AS AMENDED BY REGULATION NO 2864/72 OF THE COUNCIL OF 19 DECEMBER 1972 ( JO L 306 , P . 1 ), PROVIDES THAT ' WHERE , UNDER THE LEGISLATION OF A MEMBER STATE , ADMISSION TO VOLUNTARY OR OPTIONAL CONTINUED INSURANCE IS CONDITIONAL UPON COMPLETION OF INSURANCE PERIODS , THE INSURANCE PERIODS OR RESIDENCE PERIODS COMPLETED UNDER THE LEGISLATION OF ANOTHER MEMBER STATE SHALL BE TAKEN INTO ACCOUNT , TO THE EXTENT REQUIRED , AS IF THEY WERE INSURANCE PERIODS COMPLETED UNDER THE LEGISLATION OF THE FIRST STATE ' .
9 THE PLAINTIFF IN THE MAIN ACTION STATES THAT THE REGULARIZATION OF PERIODS OF STUDY FOR THE PURPOSE OF DETERMINING THE PENSION RIGHTS OF THE EMPLOYED PERSON IS A MATTER OF ADMISSION TO CONTINUED VOLUNTARY OR OPTIONAL INSURANCE INVOLVING THE APPLICATION OF ARTICLE 9 ( 2 ).
10 THE DEFENDANT IN THE MAIN ACTION , ON THE OTHER HAND , CONTESTED THIS STATEMENT ON THE GROUND THAT , FIRST , THE ASSIMILATION OF PERIODS OF STUDY TO PERIODS OF EMPLOYMENT DOES NOT CONSTITUTE ADMISSION TO VOLUNTARY INSURANCE AND , SECONDLY , THAT ARTICLE 9 ( 2 ) APPLIES ONLY TO PERIODS OF VOLUNTARY OR OPTIONAL INSURANCE COMPLETED AFTER A PERIOD OF COMPULSORY INSURANCE .
11 IN SUPPORT OF ITS FIRST OBJECTION THE DEFENDANT IN THE MAIN ACTION POINTS OUT THAT , APART FROM THE ASSIMILATION OF PERIODS OF STUDY TO PERIODS OF EMPLOYMENT , THERE IS UNDER BELGIAN LEGISLATION WHAT IS CALLED ' VOLUNTARY INSURANCE ' , WHERE THE METHOD USED FOR CALCULATING CONTRIBUTIONS DIFFERS FROM THAT USED FOR THE ADMISSION OF PERIODS OF STUDY AND WHERE THE RULES OF APPLICATION ALSO DIFFER .
12 A COMPARISON OF THE WORDING USED IN THE SIX OFFICIAL LANGUAGES HAS SHOWN UP VARIATIONS IN THE VERSIONS IN THE DIFFERENT LANGUAGES OF ARTICLE 9 BOTH