POWER OF ATTORNEY

    KNOW ALL MEN BY THESE PRESENTS, that the undersigned does hereby nominate,
constitute and appoint Ernest C. Jett, John A. Lyckman and John G. Moore or
the designee of any one of them, his true and lawful attorneys-in-fact, to
sign in the name of and on behalf of the undersigned and to file with the
Securities & Exchange Commission Initial Statement of Beneficial Ownership on
Form 3 and Statements of Change in Beneficial Ownership on Form 4 or Form 5
or any similar form promulgated by the Securities and Exchange Commission and
any other documents or amendments to any said statement or form, and to take
such other action, all as said attorneys-in-fact, or any one of them, deem
necessary or advisable to the end that such forms or amendments thereto be
properly and timely filed. This power of attorney shall be effective for a
period of ten years from the date hereof.

   IN WITNESS WHEREOF, the undersigned has executed this Power of Attorney
as of the 2nd day of May, 2000.

                                  /s/ RALPH W. CLARK
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                                  Ralph W. Clark