51.   The refugee problems, combined with reports of the ambush, added to a growing sense here that the effort to maintain stability faced serious obstacles.

52.   There are some serious obstacles.

53.   They faced serious obstacles.

54.   These are serious obstacles.

55.   To be sure, serious obstacles still remain.

56.   WASHINGTON - Executives for America Online Inc. and Time Warner Inc. insist their proposed merger is facing no serious antitrust obstacles.

57.   While the companies and the government can try to resurrect the deal next year, they face serious obstacles.

58.   While they stopped short of guaranteeing that the project would now proceed, city and MTA officials said that all apparent serious obstacles had been removed.

59.   Wyly faces serious obstacles, not least because he will not commit himself to buying shares in the company.

60.   Yet this enthusiasm must overcome serious obstacles.