Bellei, Giuseppe; Konstantinos Gkoumas (2010). "Transit vehicles' headway distribution and service irregularity". Public Transport. 2 (4): 269–289. doi:10.1007/s12469-010-0024-7. S2CID19725008.
Bellei, Giuseppe; Konstantinos Gkoumas (2010). "Transit vehicles' headway distribution and service irregularity". Public Transport. 2 (4): 269–289. doi:10.1007/s12469-010-0024-7. S2CID19725008.
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"Bus Clumping". The Tomes. 11 August 2007. Archived from the original on 17 March 2012. Retrieved 12 September 2011.