Hard $\gamma \gamma$ Collisions at Future $e^{+}{e}^{-}$ LINACs

We update our previous calculation of di–jet production in two–photon collisions at future \ee\ colliders, including both beam-- and bremsstrahlung. We then discuss the production of heavy ($c,b,t$) quarks. Our study re–confirms that colliders with much beamstrahlung offer no physics advantages over designs with little beamstrahlung.