21.   But the Gardners faced more serious obstacles in Washington.

22.   But this seems to represent the most serious obstacle, executives said.

23.   But while President Ernesto Zedillo agreed with President Clinton in May to negotiate such a system, Mexican officials have cautioned that they have serious legal obstacles to overcome.

24.   Congress is a serious obstacle in that regard.

25.   Despite the evidence against Ieng Sary and other leaders, independent analysts say there are serious obstacles to any eventual trial of Khmer Rouge leaders.

26.   Earlier, stocks fell as the resurgent yen cast a pall over earnings prospects at export-dependent corporations already facing serious obstacles to profit growth, traders said.

27.   Even so, time remains a serious obstacle.

28.   If the idea of a flat tax does not founder on the shoals of fairness, it faces two other serious obstacles.

29.   Indeed, if the finding is true, it could pose serious obstacles to the success of cloning.