Cambodian Rebel Drive Called Major Effort to Topple Lon Nol
several thousand Cambodian insurgents intensify offensive against Phnom Penh in what Govt and Western analysts see as âmaximum effortâ for force fall of Pres Lon Nol Govt; insurgents have penetrated within 6 miles of city and within a mile of Pochentong airport; 3,000 troops believed involved; Govt officials and foreign diplomats are skeptical of recent rumors of peace talks; Govt press says war is forgotten in the West because of oil crisis; Govt forces, with air support, meet insurgent attacks; routes to capital are reopened; map (M)