Niknejad, A. , Liaghat, G. , Behravesh, A. , Naeini, H.. "Theoretical Investigation of the Instantaneous Folding Force during the First Fold Creation in a Square Column". World Academy of Science, Engineering and Technology, Open Science Index 22, International Journal of Mechanical and Mechatronics Engineering, (2008), 2(10), 1105 - 1110.