11.   A dire plant shortage is a principal cause of the Western energy crisis.

12.   His principal cause has been to champion major, painful changes in Medicare that he believes necessary to preserve the financial viability of the system.

13.   In Oklahoma, Gov. Frank Keating, also a Republican, diagnosed divorce as a principal cause of poverty in his state.

14.   It is projected to be a principal cause of U.S. population growth.

15.   Manufactured by Interscan Corp. of Chatsworth, it monitors volatile sulfur compounds, the principal cause of chronic halitosis produced by bacteria in the mouth.

16.   No investigator has suggested that morale within the squadron was the principal cause of the crash.

17.   The accumulating evidence has convinced most critics that the Civil Rights Act was a principal cause of black progress.

18.   The principal cause of pollution is inadequate and overloaded sewage systems.

19.   The principal cause, aid workers say, is the wall of bureaucracy constructed around the Uzbekistan government, headed by President Islam Karimov.

20.   The Symington-led partnership that owned the building later lost it in the real-estate downturn that Symington claims is the principal cause of his financial collapse.