TITJUR Skalka Judgment of the Court (Fourth Chamber) of 29 April 2004. # Friedrich Skalka v Sozialversicherungsanstalt der gewerblichen Wirtschaft. # Reference for a preliminary ruling: Oberster Gerichtshof - Austria. # Social security for migrant workers - Austrian rules on compensatory supplements to retirement pensions - Classification of benefits and lawfulness of the residence requirement under Regulation (EEC) No 1408/71. # Case C-160/02.