1. 1) N. Nakajima, H. Matsuki, Tohoku-Section Joint convention, lecture number 2B15, pp75 (2008)
2. 2) T. Iwata, S. Abe, IEEJ Transactions on Industry Applications, 130, 734-741 (2010)
3. 3) M. Budhia, G. Covic and J. Boys, Proc. Annu. Conf. IEEE Ind. Electron. Soc., pp. 2487-2492 (2010)
4. 4) A. J. Moradewicz and M. P. Kazmierkowski, IEEE Trans. Ind. Electron., 59, no. 2, pp. 945-951 (2010)
5. 5) N. Jinguji, Y. Yamada, H. Matsuki, N. Hoshimiya, T. Furukawa, J.Magn. Soc. Jpn. 21, No. 4, pp693-696 (1997)