Job tenure of two cohorts of young German men 1979 - 1990 ; an analysis of the (West-)German employment statistic register sample concerning multivariate failure times und unobserved heterogeneity - Bellmann, Lutz 1956-; Bender, Stefan; Hornsteiner, Ulrich (Forschungsinstitut zur Zukunft der Arbeit <Bonn>: Discussion paper, 2000)