February 17th, 2008, 6:35 am
Refer to The Econometrics of Financial Market by John Y. Cambell. Chapter -3 Market Microstructure. You may read the author has modelled these spread biases. Though where the securities are heavily traded, you Might ignore them and take the VWAP or LTP as it is in the quote. Depends on kind of work you are into and what asset classes also.