EX‐LIA. MAN ASSAILS SAIGON EVACUATION
Former sr CIA analyst Frank Snepp, in book published by Random House called Decent Interval, says intelligence system failed in Cambodia after Govt fell in spring of '75 because CIA planners chose to focus 'stay behind' operations on central cities and cities were evacuated by Cambodians; contends officials knew for yrs that Khieu Samphan, who became Khmer Rouge post-war leader, intended to raze cities and turn soc into 'great rural estate' (M)