BALAIŠIS, P.; EIDUKAS, D.; GOČELKIENĖ, L. Electronic Payment Systems for Communications Services. Elektronika ir Elektrotechnika, [S. l.], v. 91, n. 3, p. 3-8, 2009. Disponível em: https://eejournal.ktu.lt/index.php/elt/article/view/10269. Acesso em: 2 may. 2024.