(color online) HHG power spectra with (a) and (b) by varying the peak intensity of the third-harmonic frequency-comb field. For the achievement of multiphoton resonance, (a) the CEP shift is tuned to for (black solid line), 0.101534 for (red dash line), and 0.113857 for (blue dotted line), and (b) the CEP shift is tuned to for (black solid line), 0.101703 for (red dash line), and 0.114485 for (blue dotted line). For comparison, the spectrum with is presented wit the black dash-dotted line in (a). The other parameters are the same as those in Fig. 1.