Krylovas, Aleksandras, and Joana Kastickaitė. “Experience of Test Tasks Severity Analysis: Some School Mathematics Problems Severity”. Lietuvos matematikos rinkinys 54, no. B (December 20, 2013): 123–128. Accessed November 7, 2025. https://www.zurnalai.vu.lt/LMR/article/view/17165.