If you have trouble locating any of these papers please contact an author for a reprint. A few of the later G.P. Srivastava Group papers are available as on line Postscript documents.
G P Srivastava and K Kunc
J Phys C 21, 5087-5106 (1988).
G P Srivastava, J L Martins and A Zunger
Phys Rev B 38, 12694 (1988).