U.S. AIR FORCE Sgt. Ronald Stewart died Wednesday after being seriously hurt in a bomb explosion near his home in the Glyfada suburb of Athens. . . A FORCE OF ABOUT 2,800 Cambodian government troops backed by tanks and rocket launchers attacked U.S.-supplied resistance forces in western Cambodia Wednesday in an attempt to recapture resistance "liberated zones," resistance officers said. . . INVESTIGATORS HAVE subpoenaed the owners of a Philadelphia skyscraper for information on why the building's emergency systems failed during a blaze that killed three firefighters.