1. a Electrotechnical Laboratory, MITI, 1.1.4 Umezono, Tsukuba, Ibaraki 305, Japan
2. b Electrotechnical Laboratory, MITI, 1.1.4 Umezono, Tsukuba, Ibaraki 305, Japan
3. c Electrotechnical Laboratory, MITI, 1.1.4 Umezono, Tsukuba, Ibaraki 305, Japan
4. d "Toshiba Corp., I Komukai Toshiba-cho, Saiwai-ku, Kawasaki, Kanagawa 210, Japan
5. e Electrotechnical Laboratory, MITI, 1.1.4 Umezono, Tsukuba, Ibaraki 305, Japan