51.   The United Nations considers them the main unregulated threat to the ozone layer.

52.   Today the main threats are skyrocketing crime, rampant corruption and plain old governmental ineffectiveness.

53.   Today the main external threats are from Iran, Iraq and Syria.

54.   Too swift a growth in employment could help to raise inflation, the main economic threat the Fed would fight by raising rates.

55.   Wages growth, though, remains the main threat to keeping a lid on inflation.

56.   Arab information ministers warned Wednesday that terrorism and a stalemate in Arab-Israeli peace talks are the two main threats to security and stability in the Middle East.

57.   Becker was playing strong grass-court tennis and was considered the main threat to three-time defending champion Pete Sampras.

58.   Becker was considered the main threat to Pete Sampras, the top seed and three-time defending champion.

59.   Becker had been considered the main threat to Pete Sampras, the top seed and three-time defending champion.

60.   Beijing was particularly upset that the Indian government tried to justify its tests by casting nuclear-power China as its main threat.