++++ 1. Social security for migrant workers - Legislation applicable - Single system principle - Scope - Not applicable to recipients of early retirement or supplementary pensions (Council Regulation No 1408/71, Arts 13(2) and 14 to 17) 2. Social security for migrant workers - Community rules - Matters covered - Provisions of industrial agreements - Excluded - Collection by a Member State of contributions deducted from pensions paid under industrial agreements in respect of a risk borne by another Member State - Whether permissible (Council Regulation No 1408/71, Arts 1(j) and 33)