1. Horst.-E. Vollmar, Wolfgang Drenckhahn, Stationary PEMFCs and SOFCs in the City of Tomorrow, European Fuel Cell News, vol. 5. No. 1, January 1998, pp. 17–18.
2. H.J. Beie, L. Bluhm, W. Drenckhahn, H. Greiner, H. Schichl, Development of Planar SOFC at Siemens — Status and Prospects, Proceedings of the 3rd European SOFC Forum, Nantes, France, 1998.