Santos Georgina (2005). "Urban Congestion Charging: A Comparison between London and Singapore". Transport Reviews. 25 (5): 511–534. doi:10.1080/01441640500064439. S2CID153685223.
Santos Georgina (2005). "Urban Congestion Charging: A Comparison between London and Singapore". Transport Reviews. 25 (5): 511–534. doi:10.1080/01441640500064439. S2CID153685223.