1. Transport Planning and Practice;Adams,1981
2. Adanza, E.G., 1995. Research Methods: Principles and Applications. Rex Book Store Manila, Philippines, p. 81.
3. Altares, P.S. et al. (2003). Elementary Statistics: A modern Approach. Rex Book Store Manila, Philippines, p. 13.
4. Urban Mass Transportation Planning;Black,1995
5. Buchanan, C.D., 1963. Traffic in Towns. Penguin.