\partial^{\gamma\dot{\gamma}}\partial_{\gamma\dot{\gamma}}\,\phi^{(k,n)}_{%&#10;\alpha_{1}...\alpha_{k}\,\dot{\beta}_{1}...\dot{\beta}_{n}}=2e^{2}m^{2}\,x^{%&#10;\alpha_{k+1}\dot{\beta}_{n+1}}\,x^{\alpha_{k+2}\dot{\beta}_{n+2}}\,\phi^{(k+2,%&#10;n+2)}_{\alpha_{1}...\alpha_{k}\alpha_{k+1}\alpha_{k+2}\,\dot{\beta}_{1}...\dot%&#10;{\beta}_{n}\dot{\beta}_{n+1}\dot{\beta}_{n+2}}