This excerpt taken from the IHS 10-K filed Jan 24, 2006.
14. Deferred Stock Units and Restricted Shares with Put Rights
Deferred stock units and restricted shares granted in the Offer and under the 2004 Long-Term Incentive and Directors Stock Plans (see Note 17) contained a put right on the part of the holder and a call right on the part of the Company. At November 30, 2004, redemption of the deferred stock units and restricted shares by the holders was considered uncertain as it was contingent upon certain events not occurring. If a listing event (as defined in the plan), which included an initial public offering, or a change in control, had not occurred on or prior to October 1, 2007, the put right gave the holder the option to sell to the Company, and cause the Company to purchase at fair value, all of the shares of Class A common stock of the Company owned by the holder on October 1, 2007. Similarly, if a listing event or change in control had not occurred on or prior to October 1, 2007, the call right gave the Company the exclusive one-time option to purchase from each participant, and to cause each participant to sell, at fair value, all or a portion of the shares held by him or her as of such date. However, due to the Company's November 16, 2005 initial public offering, the put and call rights terminated resulting in the reclassification of the deferred stock units and restricted shares with put rights into equity.