Abstract
The influence of the external ac electric field on the collective charge density wave transport is considered within Gor'kov's model of current oscillations. In the asymptotic limit of large dc fields (E ≳ 1) the resonances are found at E/m, i.e. at the subharmonics of the fundamental frequency. It is claimed that in the experimental range of fields (E << 1) the model gives resonances at all rational values nE/m, as was observed recently in NbSe3