WASET
    Won Taek Oh and  Adin Richard,  Critical Heights of Sloped Unsupported Trenches in Unsaturated Sand.   journal   = {International Journal of Geotechnical and Geological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2019, vol. 149(5). 317 - 324
    [viewed 18 April 2024]. Available from: https://publications.waset.org/pdf/10010329.