Small outliers and oscillations in the field dependence have no significant effect on the polarization transfer efficiency, so we smooth the field dependence by applying a Savitzky-Golay filter (Fig. .a.) The resulting curve suggests that the polarization transfer effectively occurs at least at two LACs, at about 210 nT ("LAC" 1) and at about 700 nT ("LAC" 2). However, these are not the true positions of the LACs, because, first, LACs in negative fields affect the positions of the maxima of the field dependence, and second, in such multi-spin systems it is difficult to identify LACs that are specifically responsible for polarization transfer. Nevertheless, the amplitude of the field dependence in a particular field indicates the efficiency of the polarization transfer at that point. Therefore, when sweeping the field, we intend to pass the regions of high amplitude slowly in order to satisfy the adiabaticity condition. Thus, we assume that the residence time at a certain field should be proportional to the net polarization (Fig. .b):