We calculate Adjusted EBITDA as net income before interest, taxes, depreciation and amortization, adjusted for (i) termination fees, (ii) impairment of long-lived assets, (iii) write-off of unsuccessful exploration activities, (iv) any mark-to market gains or losses from accounting for derivatives, (v) merger and acquisition transaction costs, (vi) stock-based compensation, (vii) gains or losses from extinguishment of liabilities, (viii) gains or losses on sale of subsidiaries and property, plant and equipment and (ix) other unusual or non-recurring items.