Ehab Hasan Ahmed Hasan Ali,  Establishing a New Simple Formula for Buckling Length Factor (K) of Rigid Frames Columns.   journal   = {International Journal of Civil and Environmental Engineering}, [online]. World Academy of Science, Engineering and Technology.
    January 2012, vol. 61(1). 42 - 52
    [viewed 06 May 2021]. Available from: https://publications.waset.org/pdf/9830.