1. (1) The institute of Electrical Engineers of Japan: “Electrical engineering handbook”, pp. 670-674, Denkishoin (2001-2)
2. (2) N. Ueyama, edition: “Operation and maintenance of a thyristor control DC motor”, pp. 59-67, Denkishoin (1976)
3. (3) N. Okubo: “Modal analis of machine”, pp. 168-169, Chuo University publication (1982-5)
4. (4) Association of Japanese Iron and steel, edition: “Facilities diagnosis technology handbook”, pp. 212-217, Maruzen (1988-12)
5. (5) The Institute of Electrical Engineers the Japanese Electrotechnical Committee: “JEC-TR-21003-2008 A. C. adjustable speed motors for metal rolling mills”, pp. 45-46, Denkishoin (2008-12)