1. Günterschulze, A. and Tollmien, W. Z. Phys., 119 685, 1942.
2. Wehner, G.K., J. Appl. Phys. 30 1762 1959.
3. Cheney, K.B. and Pitkin, E.T. J. Appl. Phys. 36 3542, 1965.
4. Witcomb, M.J. Rad. Effects. 27 223,1976.
5. Yamamusa, Y., Itikawa, Y and Itoh, N. Report IPPJ-AM-26, Nagoya University, Nagoya, Japan, 1983.