This excerpt taken from the ELN 6-K filed Apr 11, 2005.
q Stock compensation
Stock option compensation expense is the difference between the market value of shares at the date of the option grant and the amount of the consideration, if any, that participants may be required to pay for the shares. The intrinsic cost of awards to employees that take the form of shares or rights to shares are recognised over the period of the employees related performance. Where there are no performance criteria, the cost is recognised over the period from the date of the award to the date at which the employee becomes unconditionally entitled to the shares.