@bookHehenkamp_Kaarbøe, title=Price Regulation, Quality Competition and Location Choice with Costly Relocation, author=Hehenkamp, Burkhard and Kaarbøe, Oddvar M. 

@bookEndres-Fröhlich_Hehenkamp_Heinzel, title=The Impact of Product Differentiation on Retail Bundling in a Vertical Market, author=Endres-Fröhlich, Angelika Elfriede and Hehenkamp, Burkhard and Heinzel, Joachim