Before revision:  The sources of multifractality are also investigatedand it is confirmed that both temporal correlation and the fat-tailed distribution contribute to the multifractality, and the degree of multifractality for the temporal correlation is stronger than thatfor the fat-tailed distribution .
After revision:  The sources of multifractality are investigated, confirming that both temporal correlation and the fat-tailed distribution contribute to the multifractality, and the degree of multifractality for the temporal correlation is stronger than thatfor the fat-tailed distribution .