Operating cash flow, adjusted EBITDA, adjusted net income available to common stockholders and PV-10 are non-GAAP financial measures.

The company defines operating cash flow as net cash provided by operating activities before changes in operating assets and liabilities. It defines EBITDA as net (loss) income before income tax (benefit) expense, interest expense and depreciation, depletion and amortization. Adjusted EBITDA, as presented herein, is EBITDA excluding interest income, gain or loss on the sale of assets and other various non-cash items (including asset impairments, income from equity investments, noncontrolling interest, stock-based compensation, unrealized (gain) loss on derivative contracts and provision for doubtful accounts). This definition of adjusted EBITDA generally conforms to the EBITDA definition in the company’s credit agreement.

Operating cash flow and adjusted EBITDA are supplemental financial measures used by the company’s management and by securities analysts, investors, lenders, rating agencies and others who follow the industry as an indicator of the company’s ability to internally fund exploration and development activities and to service or incur additional debt. The company also uses these measures because operating cash flow and adjusted EBITDA relate to the timing of cash receipts and disbursements that the company may not control and may not relate to the period in which the operating activities occurred. Further, operating cash flow and adjusted EBITDA allow the company to compare its operating performance and return on capital with those of other companies without regard to financing methods and capital structure. These measures should not be considered in isolation or as a substitute for net cash provided by operating activities prepared in accordance with generally accepted accounting principles ("GAAP"). Adjusted EBITDA should not be considered as a substitute for net income, operating income, cash flows from operating activities or any other measure of financial performance or liquidity presented in accordance with GAAP. Adjusted EBITDA excludes some, but not all, items that affect net income and operating income and these measures may vary among other companies. Therefore, the company’s adjusted EBITDA may not be comparable to similarly titled measures used by other companies.

Management also uses the supplemental financial measure of adjusted net income available (loss applicable) to common stockholders, which excludes asset impairments, unrealized (loss) gain on derivative contracts and gain or loss on the sale of assets from net income available (loss applicable) to common stockholders. Management uses this financial measure as an indicator of the company’s operational trends and performance relative to other oil and natural gas companies and believes it is more comparable to earnings estimates provided by securities analysts. Adjusted net income available (loss applicable) to common stockholders is not a measure of financial performance under GAAP and should not be considered a substitute for net income available (loss applicable) to common stockholders.

PV-10 represents the present value of estimated future cash inflows from proved natural gas and oil reserves, less future development and production costs, discounted at 10% per annum to reflect timing of future cash flows and using pricing assumptions in effect at the end of the period for periods prior to December 31, 2009 and 12-month average prices for the year ended December 31, 2009. PV-10 differs from Standardized Measure because it does not include the effects of income taxes on future net revenues. Management uses PV-10 as an arbitrary reserve asset value measure to compare against past reserve bases and the reserve bases of other business entities that are not dependent on the tax-paying status of the entity.

Operating cash flow, adjusted EBITDA, adjusted net income available to common stockholders and PV-10 are non-GAAP financial measures.

The company defines operating cash flow as net cash provided by operating activities before changes in operating assets and liabilities. It defines EBITDA as net (loss) income before income tax (benefit) expense, interest expense and depreciation, depletion and amortization. Adjusted EBITDA, as presented herein, is EBITDA excluding interest income, gain or loss on the sale of assets and other various non-cash items (including asset impairments, income from equity investments, noncontrolling interest, stock-based compensation, unrealized (gain) loss on derivative contracts and provision for doubtful accounts). This definition of adjusted EBITDA generally conforms to the EBITDA definition in the company’s credit agreement.

Operating cash flow and adjusted EBITDA are supplemental financial measures used by the company’s management and by securities analysts, investors, lenders, rating agencies and others who follow the industry as an indicator of the company’s ability to internally fund exploration and development activities and to service or incur additional debt. The company also uses these measures because operating cash flow and adjusted EBITDA relate to the timing of cash receipts and disbursements that the company may not control and may not relate to the period in which the operating activities occurred. Further, operating cash flow and adjusted EBITDA allow the company to compare its operating performance and return on capital with those of other companies without regard to financing methods and capital structure. These measures should not be considered in isolation or as a substitute for net cash provided by operating activities prepared in accordance with generally accepted accounting principles ("GAAP"). Adjusted EBITDA should not be considered as a substitute for net income, operating income, cash flows from operating activities or any other measure of financial performance or liquidity presented in accordance with GAAP. Adjusted EBITDA excludes some, but not all, items that affect net income and operating income and these measures may vary among other companies. Therefore, the company’s adjusted EBITDA may not be comparable to similarly titled measures used by other companies.

Management also uses the supplemental financial measure of adjusted net income available (loss applicable) to common stockholders, which excludes asset impairments, unrealized (loss) gain on derivative contracts and gain or loss on the sale of assets from net income available (loss applicable) to common stockholders. Management uses this financial measure as an indicator of the company’s operational trends and performance relative to other oil and natural gas companies and believes it is more comparable to earnings estimates provided by securities analysts. Adjusted net income available (loss applicable) to common stockholders is not a measure of financial performance under GAAP and should not be considered a substitute for net income available (loss applicable) to common stockholders.

PV-10 represents the present value of estimated future cash inflows from proved natural gas and oil reserves, less future development and production costs, discounted at 10% per annum to reflect timing of future cash flows and using pricing assumptions in effect at the end of the period for periods prior to December 31, 2009 and 12-month average prices for the year ended December 31, 2009. PV-10 differs from Standardized Measure because it does not include the effects of income taxes on future net revenues. Management uses PV-10 as an arbitrary reserve asset value measure to compare against past reserve bases and the reserve bases of other business entities that are not dependent on the tax-paying status of the entity.