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. DOI: 10.5755/j02.eie.10269. Disponível em: https://eejournal.ktu.lt/index.php/elt/article/view/10269.. Acesso em: 11 jun. 2026.