00325nam a2200097 a 450000500170000008200200001710000230003724501110006026000350017130000210020620251203091555.0  a512.55,bD, hel  aHelgason, Sigurdur  aGroups and geometric analysis: Integral geometry, invariant differential operators and spherical functions  aNew YorkbAcademic pressc1984  axx, 654p, 22 cm.