A. Ganczarski and J. Lenczowski, “On the convexity of the Goldenblat-Kopnov yield condition”, Arch. Mech., vol. 49, no. 3, pp. 461–475, Jan. 1997, Accessed: Jan. 17, 2026. [Online]. Available: http://am.ippt.gov.pl/index.php/am/article/view/v49p461