1. H. Saito et al. Proc. CLEC ’85, paper WM30, pg.120.
2. W.B. Jones Laser Focus / Electro Optics Sept. ’83.
3. C.H. Sugawara et al. Proc. CLEC ’84, paper TUC3, pg.54.
4. M. Karasatsu et al. Proc. CLEC ’8l, paper WE7, pg.4
5. W.L. Nighan Phys. Rev. A2, 1989, 1970