B. Meyer, G. Ewerhart, and T. Siebe, “Tertiarisation without a competitive industrial base? An empirical analysis of shifts in the sectoral structure of employment in the münsterland and in the emscher-lippe region”, RuR, vol. 57, no. 5-6, pp. 386–397, Sep. 1999, doi: 10.1007/BF03184507.