11.   Also in question is the thorny problem of sovereign immunity.

12.   And Cohen must deal with another thorny problem as well.

13.   As the U.S. military grapples with the thorny problem of sex within its ranks, the Air Force stands out in aggressively targeting its own for adultery.

14.   At UMass, Rossini has been working for years on the thorny problem of how to achieve tolerance, or the state in which islet cells would be accepted.

15.   Addison Schonland from CIC Research points out that if airline fares are put on the Internet, the thorny problem of arbitrage could emerge.

16.   Actors playing Richard or Iago inevitably come across the thorny old problem of motive.

17.   Additionally, some longtime computer designers are beginning to use asynchronous logic to solve thorny problems.

18.   Brown acknowledged that it is a thorny problem, but one that needs to be addressed more by the county, not the city.

19.   But there remained the thorny problem of correcting for factors other than the hormone therapy that might account for the results.

20.   But thorny problems remain in Sino-American relations as well as in the establishment of any firmly democratic institutions in China itself.