APYNIS, Antanas; STANKUS, Eugenijus. Mathematics in economics and business studies. Lietuvos matematikos rinkinys, [S. l.], v. 42, n. spec., p. 353–354, 2002. DOI: 10.15388/LMR.2002.32930. Disponível em: https://www.journals.vu.lt/LMR/article/view/32930.. Acesso em: 17 jul. 2024.