1. (1) R. R. Schmidt, C. Belady, A. Classen, T. Davidson, M. K. Herrlin, S. Novotny, and R. Perry: “Evolution of Data Center Environmental Guidelines, ASHRAE Transactions”, Vol. 110, Part1, pp. 559-566 (2004)
2. (2) Ministry of Internal Affairs and Communications, Japan: “2014 White Paper Information and Communications in Japan” (2014)
3. (3) T. Babasaki, T. Tanaka, Y. Nozaki, T. Tanaka, T. Aoki, and F. Kurokawa: “Developing of Higher Voltage Direct-Current Power-feeding Prototype System”, Proceedings of the International Tele-communications Energy Conference (INTELEC), Incheon, Korea, pp. 1-5 (2009)
4. (4) Y. Sugiyama: “Green ICT toward Low Carbon Society”, Design for Innovative Value Towards a Sustainable Society, Proceedings of EcoDesign 2011, 7th International Symposium on Environmentally Conscious Design and Inverse Manufacturing, pp. 739-742 (2011)
5. (5) T. Ninomiya, Y. Ishizuka, R. Shibahara, and S. Abe: “Energy-Saving Technology Using Next-Generation Power Electronics”, Proceedings of the IEE-Japan Industry Applications Society Conference, Chiba, Japan, No. 1-S5-5, pp. I 15-I 20 (2012) (in Japanese)