21.   Most of the major antivirus packages allow online updates for a specified time after purchase.

22.   Note that travel vouchers often have to be used within a specified time and sometimes only by you.

23.   Options give the holder the right, but not the obligation, to purchase stock at a predetermined price during a specified time period.

24.   Others, like Eugene, Ore., ticket vehicles that pass a designated sign more than two times in a specified time.

25.   Purchasers must promise to install additional capacity within specified time periods.

26.   Smart mines, which automatically deactivate or self-destruct after a specified time, would be allowed to remain in the U.S. arsenal for several more years.

27.   Swap contracts typically involve an exchange of payments between two parties for a specified time period.

28.   The appropriately named Disappearing Inc. has come up with software that automatically makes sensitive or personal e-mail unreadable after a specified time.

29.   The central bank tried to prop up the currency by buying forward contracts, committing it to buy baht at a specified time and price.

30.   The call is made according to a random pacing schedule if the customer has no preference, or at the specified calling time if he does.