Nahla H. Alaswadko and  Rayya A. Hassan and  Bayar N. Mohammed,  Empirical Roughness Progression Models of Heavy Duty Rural Pavements.   journal   = {International Journal of Civil and Environmental Engineering}, [online]. World Academy of Science, Engineering and Technology.
    February 2018, vol. 135(3). 301 - 307
    [viewed 08 March 2021]. Available from: https://publications.waset.org/pdf/10008714.