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.
R A H Hamilton and G P Srivastava
Phonon Scattering in Solids (Eds Challis, Rampton and Wyatt, Plenum Press, New York 1975) 370-374