Before revision:  We then analyze the PDF of normalized relative price levels by removing the factor of order numbers stored at the price level, and find that the PDF has a power-law behavior in the tails for both buy and sell orders.
After revision:  We then analyze the PDF of normalized relative price levels by removing the factor of order numbers stored at the price level, we find that the PDF has a power-law behavior in the tails for both buy and sell orders.