Initial Statement of Beneficial Ownership (3)

EXHIBIT 24

LIMITED POWER OF ATTORNEY 

The undersigned hereby constitutes and appoints each of Kristin M. Coleman and
Deann M. Bogner, 
with full power to each of them to act alone, as his true and lawful
attorney-in-fact to:

(1) execute and file in the name and on behalf of the undersigned Forms 3, 4 and
5 
pursuant to 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, the NASDAQ Stock
Market, or 
otherwise; and

(3) take any other action of any type whatsoever in connection with the
foregoing which such 
attorney-in-fact in his or her sole discretion determines 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 the
Power of Attorney 
shall be in such form and shall contain such terms and conditions as such
attorney-in-fact may 
approve in his or her discretion.

Until such time as the undersigned is no longer subject to the obligations
imposed by Section 16, 
the undersigned hereby grants to each such attorney-in-fact full power and
authority to do and 
perform each and every act and thing whatsoever which such attorney-in-fact in
his or her sole 
discretion determines to be necessary or appropriate to be done in the exercise
of any of the 
rights and powers herein granted, with full power of substitution or
resubstitution, hereby 
ratifying and confirming all that such attorney-in-fact, or his or her
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 
and shall have no liability with respect thereto.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 
19th day of August, 2015.


/s/ Lynn Pendergrass
Lynn Pendergrass