by (USSR)A.Yariv;by (United Kingdom)J.M.Ziman; by (USSR)V.A.Ugarov;by (United Kingdom)C.M.Will; by (USSR)A.Starkov;by (United Kingdom)A.Sharp; by (USSR)V.M.Potapov;by (United Kingdom)O.B.Ramasy; by (United States)M.A.Omar;by (United Kingdom)J.M.Ziman; by (USSR)I.V.Petrynov;by (United Kingdom)J.G.Stark; by (USSR)M.L.Krasnov;by (United Kingdom)L.M.Delves; by (USSR)M.Vygodsky;by (United Kingdom)J.L.Bell; by (USSR)A.Y.Lebedeva;by (United Kingdom)R.Courtney; by (USSR)A.A.Logunov;by (United Kingdom)W.Heisenberg;