Religiosity as a Determinant of Happiness (with Matthias Opfinger). Leibniz University Hannover, Discussion Paper, 467, March 2011.
The agricultural, demographic, and democratic transitions (with Martin Paldam). Two estimation models giving reverse results. Mimeo, Aarhus and Hamburg, September 2010.
Technology differences in empirical studies of international trade (with Albert de Vaal). Mimeo, Hamburg and Nijmegen, April 2011.
The Religious Transition. A Long-run Perspective (with Martin Paldam). Kiel Working Paper, 1576, December 2009 (revised April 2011).