TY - JOUR A1 - Wagner, G.G. A1 - Frick, J.R. A1 - Schupp, J. T1 - The German Socio-Economic Panel Study (SOEP): Scope, evolution and enhancements Y1 - 2007 DO - 10.2139/ssrn.1028709 JF - Schmollers Jahrbuch VL - 127 ER -