A longitudinal undulating electric field in the lasing electron beam direction (or the longitudinal direction) and an electromagnetic wave propagating in the longitudinal direction (laser wave) drive a current that cannot be in the longitudinal direction. Thus this current can emit an electromagnetic wave having the same wave vector and polarization vector as those of the incident electromagnetic wave. This process is called stimulated bremsstrahlung in the longitudinal electric wiggler. Because of recent strong interest in this free electron lasing mechanism, it is appropriate to correct errors in numerical factors in the gain formula and equations in our paper.