F. Mansor, N., et al. “Bus Driver Scheduling and Rostering: Maximise Fairness Using Enhanced Harmony Search Algorithm With Varieties of Step Functions and Fret Spacing Formula”. International Journal of Engineering and Technology, vol. 7, no. 3.28, Aug. 2018, pp. 136-43, https://doi.org/10.14419/ijet.v7i3.28.24682.