Exhibit 23.1
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
We hereby consent to the incorporation by reference in the Registration Statement on Form S-3 (No. 333-185398), and S-8 (No. 333-169338) of our report dated February 25, 2013, except with respect to our opinion on the consolidated financial statements insofar as it relates to the change in segments described in Note 14 as to which the date is July 15, 2013, relating to the financial statements and the effectiveness of internal control over financial reporting, which appear in this Current Report on Form 8-K dated July 15, 2013.
/s/ PricewaterhouseCoopers LLP
Tulsa, Oklahoma
July 15, 2013