ANDIRKONIS, Julius. Loop-free sequent calculus for modal logic K4. Lietuvos matematikos rinkinys, [S. l.], v. 50, n. proc. LMS, p. 241–246, 2009. DOI: 10.15388/LMR.2009.43. Disponível em: https://www.journals.vu.lt/LMR/article/view/17971.. Acesso em: 16 aug. 2024.