1. J. Wesson, Tokamaks, 2nd ed. (Oxford University Press, New York, 1997), p. 109.
2. M. Wakatani, Stellarator and Heliotron Devices (Oxford University Press, New York, 1998), p. 8.
3. R. C. Davidson, Physics of Nonneutral Plasmas (Addison-Wesley, Redwood City, CA, 1990), p. 42.
4. Z. Yoshida, Y. Ogawa, J. Morikawa et al., in Non-neutral Plasma Physics III, AIP Conf. Proc. No. 498, edited by J. J. Volinger, R. L. Spencer, and R. C. Davidson (AIP, Melville, NY, 1999) p. 397.