Box-counting log_e N vs. − log_e L of Pleiades and NGC 3532. The slopes of the red solid lines fitted by robust regression represent the estimated fractal dimension f_dim. The intervals defined by the vertical dashed lines correspond to the fitting range [− log_e 2, log_e 2]. The horizontal dashed line in each panel indicates the natural logarithm of the total number of member stars in the respective star clusters.