1. S. C. Davis, S. W. Diegel, Transportation Energy Data Book, Edition 26, Oak Ridge National Laboratory, Oak Ridge, TN, USA, 2007.
2. DOE Multiyear Program Plan (Table 3.4.2) can be found under http://www1.eere.energy.gov/hydrogenandfuelcells/mypp/pdfs/fuel_cells.pdf, 2007.
3. M. Debe, U.S. Department of Energy Hydrogen Program, 2008 Annual Merit Review Proceedings, can be found under http://www.hydrogen.energy.gov/pdfs/review08/fc_1_debe.pdf.
4. K. Wipke, S. Sprik, J. Kurtz, U.S. Department of Energy Hydrogen Program, 2008 Annual Merit Review Proceedings, can be found under http://www.hydrogen.energy.gov/pdfs/review08/tv_5_wipke.pdf.
5. C. K. Mittelsteadt, W. Braff, M. Chen, S. Van Blarcom, H. Liu, U.S. Department of Energy Hydrogen Program, 2008 Annual Merit Review Proceedings, can be found under http://www.hydrogen.energy.gov/pdfs/review08/fc_24_mittelsteadt.pdf or C. Mittelsteadt, U.S. Department of Energy 2008 Annual Progress Report.