1. Y. Saitoh and W. Yokota, Proceedings of the 7th Symposium on Beam Engineering of Advanced Material Syntheses, 1996, p. 131.
2. K. S. Golovanivsky, Proceedings of the 12th International Workshop on ECR Ion Sources, 1995, p. 329.
3. Z. Q. Xie and G. W. Lyneis, Proceedings of the 12th International Workshop on ECR Ion Sources, 1995, p. 24.