1. (1) O. Oda: “Study on Wear of Contact Wire and Contact Strip on Shinkansen”, RTR Report, No. 1323 (1986) (in Japanese)
2. (2) F. Nakama, M. Ichikawa, and H. Nagasawa: “Measurement of Contact Loss by Detecting Spark”, RTR Report, No. 1251 (1983) (in Japanese)
3. (3) M. Shimizu: “Development of a Optical Fiver Type Measuring Instrument of Arc Light”, Proc. of the 1966 National Convention IEEJ Conference, No. 5, pp. 395-396 (1995) (in Japanese)