We define free cash flow as net cash provided by operating activities less purchases of property, plant and equipment. Free cash flow is not defined by U.S. generally accepted accounting principles ("U.S. GAAP"). We believe free cash flow to be relevant and useful information to our investors because it provides them with additional information in assessing our liquidity, capital resources and financial operating results. Our management uses free cash flow in evaluating our liquidity, our ability to service debt and our ability to fund capital additions. However, free cash flow has certain limitations, including that it does not represent the residual cash flow available for discretionary expenditures since other, non-discretionary expenditures, such as mandatory debt service, are not deducted from the measure. The amount of mandatory versus discretionary expenditures can vary significantly between periods. This measure should be considered in addition to, and not as a substitute for, or superior to, other measures of liquidity or financial performance prepared in accordance with U.S. GAAP, such as net cash provided by operating activities. Furthermore, our definition of free cash flow may not be comparable to similarly titled measures reported by other companies.

The potential shares of common stock and interest related to the 6.0% convertible notes due 2014 were excluded from earnings per diluted share for the three months ended June 30, 2012, because the effect of including these potential shares was antidilutive.