“…An elegant and popular method in stock market network analysis is to employ minimal or maximal spanning tree methods to find a “backbone” of the full correlation network [ 8 , 9 , 11 , 26 , 27 , 28 ]. Several more complicated correlation matrix construction and filtering methods have been developed recently [ 23 , 25 , 29 , 30 , 31 , 32 , 33 ], but utilizing these methods is left for future research.…”