[1] Μ. Panish, I. Hayashi et al; Αρρl. Phys. Lett., 1970,16,326.
[2] P. Petroff, R. Hartman; Apph Phys. Lett., 1973, 23, 469.
[3] Appl. Phys. Lett.,1977,31,No. 11, 756.
[4] IEEE J. Quant. Electr., 1978,QE-14, 89.
[6] Appl. Phys. Lett., 1978, 32, 5.
[7] P. Petroff, R. Hartmac; Appl. Phys. Lett.,1973, 23,469.
[8] P. Hutchinson et al.,Phil. Mag., 1975, 32,7450