POWER OF ATTORNEY

     Know all by these presents, that the undersigned hereby constitutes and
appoints each of Joan Hague and Javier Solis, signing singly, his true and
lawful attorney-in-fact to:

(1)  execute for and on behalf of the undersigned Forms 3, 4 or 5 and in
     accordance with Section 16(a) of the Securities Exchange Act of 1934 and
     the rules thereunder;

(2)  do and perform any and all acts for and on behalf of the undersigned which
     may be necessary or desirable to complete the execution of any such Form 3,
     4 or 5 and the timely filing of such form with the United States Securities
     and Exchange Commission and any other authority; and

(3)  take any other action of any type whatsoever in connection with the
     foregoing which, in the opinion of such attorney-in-fact, may be of benefit
     to, in the best interest of, or legally required by, the undersigned, it
     being understood that the documents executed by such attorney-in-fact on
     behalf of the undersigned pursuant to this Power of Attorney shall be in
     such form and shall contain such terms and conditions as such
     attorney-in-fact may approve in his discretion.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform all and every act and thing whatsoever requisite,
necessary and proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as such attorney-in-fact
might or could do if personally present, with full power of substitution or
revocation, hereby ratifying and confirming all that such attorney-in-fact, or
his substitute or substitutes, shall lawfully do or cause to be done by virtue
of this power of attorney and the rights and powers herein granted. The
undersigned acknowledges that the foregoing attorneys-in-fact, in serving in
such capacity at the request of the undersigned, are not assuming any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

Unless rescinded earlier in writing, this Power of Attorney will expire on July
1, 2008.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 30th day of_June, 2003


                                    Signature:       /s/ James S. Marlen