Nurullayev Н., Turgunboyev Д., and Zholdassov Е. “EVALUATION OF POSSIBILITIES TO IMPROVE RIGID BODIES”. Bulletin of Abai KazNPU. Series of Physical and Mathematical Sciences, vol. 69, no. 1, June 2021, pp. 392-5, https://bulletin-phmath.kaznpu.kz/index.php/ped/article/view/238.