The tunneling effect of the Cooper pairs in a superconductor-insulator-superconductor-insulator-superconductor structure is analyzed by Feynman-like method, and the equations describing the electric current are obtained. For the case when both junctions are in the zero voltage state, the exact solution of the equations is obtained. It is found that, because of the tunneling effect of the Cooper pairs, an alternating current exists which can be expressed by an elliptic function. And then, on second thoughts, the conclusion that the SISIS cannot emit electromagnetic radiation when both junctions...
