$e^{+}{e}^{-}\to b\bar{b}{W}^{+}{W}^{-}$ at the Next Linear Collider, Top-Pairs and Higgs Production

The complete matrix element for $e^{+}{e}^{-}\text{ar}{W}^{+}{W}^{-}\bar{b}b$ is computed at tree level and applied to: {\bf a)} $\bar{t}t$ production and decay ; {\bf b)} $ZH$ production followed by $Z\text{ar}\bar{b}b$ and $H\text{ar}WW$. In both cases we include finite width effects and all irreducible backgrounds.