++++ 1. Social security for migrant workers ° Unemployment ° Employed person insured, pursuant to an agreement between the competent authorities, in a Member State other than the Member State of employment and residence ° Applicability of Article 71(1)(b)(ii) of Regulation No 1408/71 (Council Regulation No 1408/71, Arts 17 and 71(1)(b)(ii)) 2. Social security for migrant workers ° Legislation applicable ° Determination by agreement between Member States ° Retroactive effect ° Whether permissible (Council Regulation No 1408/71, Arts 17 and 71(1)(b)(ii))