Bolometric luminosity k_bol vs. bolometric stretch factor s_bol for the 17 GRB SNe listed in Table 2. Red-colored data points refer to the four GRB SNe discussed here, black-colored data points to the remaining 13 events. We note that SN 1998bw is not included here (by definition, ). The best fit is shown for an ansatz , a = 1.7 (excluding in the fit GRBs 111209A, 111228A and SN 1998bw).