Seyyed Abolhasan Naeini and  Ehsan Azini,  Investigation of Slope Stability in Gravel Soils in Unsaturated State.   journal   = {International Journal of Geotechnical and Geological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    May 2019, vol. 150(6). 471 - 474
    [viewed 19 October 2019]. Available from: https://publications.waset.org/pdf/10010514.