0 BTM102:VIETNAM-ANNIVERSARY;SAIGON,VIETNAM,24APR95 -FILE PHOTO APR75- Their backs to the wall, evacuees are helped aboard an Air America helicopter perched atop a Saigon building April 29,1975.The evacuation site was one of many in the downtown area from which Americans and foreign nationals were evacuated to waiting Navy ships. April 1995 marks the 20th anniversary of the fall of Saigon to the communists and the end of the Vietnam war. cm/FLS-Hubert Van Es REUTER/BETTMANN published in nyt 04/30/95