Helbrecht, Ilse, and Tim Geilenkeuser. “Demographic Change, Generation Effects and Housing Markets: Homeownership As Pension?”. Raumforschung Und Raumordnung | Spatial Research and Planning, vol. 70, no. 5, Oct. 2012, pp. 425–436, https://doi.org/10.1007/s13147-012-0185-8.