Notice of annual meeting of stockholders
April 19, 2012

Dear Stockholder:

You are cordially invited to attend the 2012 annual meeting of stockholders on Thursday, April 19, 2012, at the cafeteria on our property at 12500 TI Boulevard, Dallas, Texas, at 10:00 a.m. (Dallas time). At the meeting we will consider and act upon the following matters:

• the election of directors for the next year,
• advisory approval of the company’s executive compensation,
• ratification of the appointment of Ernst & Young LLP as the company’s independent registered public accounting firm for 2012, and
• such other matters as may properly come before the meeting.

Stockholders of record at the close of business on February 21, 2012, are entitled to vote at the annual meeting.

We urge you to vote your shares as promptly as possible by: (1) accessing the Internet website, (2) calling the toll-free number or (3) signing, dating and mailing the enclosed proxy. 

Sincerely,

Joseph F. Hubach

Senior Vice President,

Secretary and

General Counsel

Dallas, Texas
March 6, 2012