 In the linear approximation we derive mean square price and volatility } disturbances as functions of the first and second-degree trades disturbances.
<meaning-changed>  In the linear approximation we derive mean square price and volatility } disturbances as functions of the first and second-degree trades disturbances.
 In the linear approximation we derive mean square price and volatility \sigma} disturbances as functions of the first and second-degree trades disturbances.