Supersymmetric Box Contributions to $ e^+ e^- \to Z^0 h^0 $ and $ e^+ e^- \to A^0 h^0 $

Within the MSSM we calculate the electroweak 1-loop box contributions to the processes $e^+ e^- \rightarrow Z^0 h^0$ and $e^+ e^- \rightarrow A^0 h^0$. We present detailed results for c. m. energies $\sqrt{s}=200$ GeV and $\sqrt{s}=500$ GeV as well as for $\tan\beta=2$ and $\tan\beta=50$. The box contributions to the process $e^+ e^- \rightarrow Z^0 h^0$ are, depending on $\sqrt{s}$ and $\tan\beta$, of the order -2 to -20\% and to $e^+ e^- \rightarrow A^0 h^0$ of 2 to 10\%.