\partial^{\gamma\dot{\gamma}}\partial_{\gamma\dot{\gamma}}\,\phi^{(k,n)}_{%
\alpha_{1}...\alpha_{k}\,\dot{\beta}_{1}...\dot{\beta}_{n}}=2e^{2}m^{2}\,x^{%
\alpha_{k+1}\dot{\beta}_{n+1}}\,x^{\alpha_{k+2}\dot{\beta}_{n+2}}\,\phi^{(k+2,%
n+2)}_{\alpha_{1}...\alpha_{k}\alpha_{k+1}\alpha_{k+2}\,\dot{\beta}_{1}...\dot%
{\beta}_{n}\dot{\beta}_{n+1}\dot{\beta}_{n+2}}