Linear fitting of GRBs. The black solid line represents the fitting result in log–log field. The red dotted and dashed lines represent ﹩1{\sigma }_{v}﹩ and 2σv regions of extra variabilities, and the gray area stands for a 95% confidence interval of fitting uncertainties. The four red points located far outside of the 2σv region are GRB 111005A, GRB 080517, GRB 101225A, and GRB 171205A.