Belovas, Andrejus, and Stanislovas Norgėla. “Sequent Calculus Sk4 for Skolemized Formulas”. Lietuvos matematikos rinkinys 45, no. spec. (December 18, 2005): 316–320. Accessed November 16, 2025. https://www.zurnalai.vu.lt/LMR/article/view/26672.